Effect of stage of anestrus on the induction of estrus by the dopamine agonist cabergoline in dogs

Beagle bitches were administered the dopamine D2 receptor agonist cabergoline in 3 groups of 5 animals each, starting on known days of the estrous cycle. Cabergoline treatment was started in either early anestrus (Days 93 to 108), mid-anestrus (Days 123 to 156), or late anestrus (Days 161 to 192) at doses of 5 ug/kg/d, per os, and was continued until the confirmation of induced proestrus or for 40 d. Reproductive parameters were compared with those in 5 control anestrous bitches (Days 90 to 150). In control bitches, the mean (+/- SEM) interval to the next proestrus (73+/-11 d) resulted in an interestrus interval (192+/-9 d) similar to that of the previous cycles (196+/-11 d). In 14 of the 15 cabergoline-treated bitches, the next proestrus occurred within 4 to 30 d, was premature in early and mid-anestrous bitches and developed with low variability within groups. The resulting intervals to proestrus in bitches treated with cabergoline in early anestrus (20+/-2 d), mid-anestrus (14+/-3 d) and late anestrus (6+/-1 d) resulted in interestrus intervals in those groups of 131+/-5, 166+/-7 and 196+/-2 d, respectively. In response to treatment, interestrus intervals were reduced (P<0.05) and more synchronous (P<0.05) in early and mid-anestrus bitches, and were more synchronous (P<0.05) in late-anestrous bitches compared with those of control bitches or those of the previous cycle. Periovulatory estradiol and progesterone profiles of induced cycles in treated bitches were similar to those of spontaneous cycles in control bitches. Four of 5 control bitches and 12 of the 14 responding cabergoline-treated bitches became pregnant and produced normal litters. Plasma prolactin concentrations at Days 2 and 5 of treatment (0.3+/-0.1 ng/mL) and at the onset of proestrus shortly before the end of treatment (0.4+/-0.1 ng/mL) were lower (P<0.05) than those present in anestrus prior to treatment (1.7+/-0.6 ng/mL) or in control bitches. Prolactin was also low at the onset of proestrus in control bitches (0.5+/-0.2 ng/mL). The results demonstrate that prolactin-lowering doses of the dopamine agonist cabergoline can terminate the normal obligate anestrus in dogs, and that the effect occurs more slowly in early anestrus than in mid or late anestrus.     

Induction of estrus in bitches with normal and persistent anestrus using human menopausal gonadotropin (hMG)

Human menopausal gonadotropin (hMG) was administered intramuscularly to 10 bitches during apparently normal anestrus (n = 7) or persistent anestrus (n = 3). Each dog received a 75-IU dose of hMG (75 IU LH and 75 IU FSH; 1 to 7 units/kg) daily for nine days. Nine bitches responded with obvious signs of proestrus within 3 to 9 days. Of these, 3 bitches exhibited a weak proestrus while 2 exhibited a normal estrus and ovulation but failed to become pregnant The remaining 4 bitches became pregnant at the induced cycle and produced normal litters at 72 to 85 d after the start of treatment, including 1 bitch that had been treated at 24 mo after the last estrus. In 2 cases, treatment resulted in ovulation following 25 or 34 mo of chronic pubertal anestrus, 1 of which became pregnant. The results suggest that hMG can be a useful gonadotropin preparation for inducing estrus in dogs.     

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.     

Effects of dose and duration of continuous GnRH-agonist treatment on induction of estrus in beagle dogs: competing and concurrent up-regulation and down-regulation of LH release

Dose-response estrus-induction trials were conducted during anestrus in 93 treated and 6 control bitches, a continuous administration of the GnRH-agonist lutrelin with a potency 150 x GnRH, and at six different doses from 0.2 to 4.8 microg/kg/d for 7-14 days in 15 groups of six to eight dogs each in defined stages of natural or pharmacologically determined anestrus. Agonist treatment induced clinically and cytologically normal proestrus (in 89% of cases) within 4.8 +/- 0.2 x days, and resulted in behavioral estrus (71%), spontaneous late-proestrus LH (and FSH) surges, ovulation (59%) and pregnancy (44%) in a dose dependent manner. Outcomes of ovulation and pregnancy in most cases required that the dose be sufficiently large enough to routinely stimulate a large initial increase in LH and FSH (i.e., > or = 0.6 microg/kg/d), and of sufficient duration (i.e., > 7 days) to ensure that supra-basal gonadotropin levels persistedntil no longer needed for spontaneous continuation of an induced proestrus. Success additionally required that the GnRH dose be modest enough (i.e., < 1.8 microg/kg/d) to not excessively down-regulate spontaneous pre-ovulatory surge release of gonadotropin or be removed shortly before or at the time when the LH surges typically occurred (10-13 days after initiation of treatment). The 1.8 microg dose was compared to saline to assess the time course of its down-regulation action on serum LH in six ovariohysterectomized bitches compared to four saline-related controls. Results in intact bitches receiving the 1.8-microg doses demonstrated an LH-releasing effect for 10-11 days that overlapped a period of obvious down-regulation seen with the same dose after 3 days in the ovariohysterectomized bitches. In the latter, however, complete down-regulation to anestrus-like values did not occur until after 18-21 days of treatment. A dose of 0.6 microg/kg/d for 12 days yielded the best estrus-induction results, including pregnancy rates of 100% in six bitches treated in natural-anestrus bitches, six bitches in which anestrus had been advanced by a luteolytic prostaglandin treatment and in six bitches in which anestrus had been extended by progesterone implants administered for 3 months. Although lutrelin is not commercially available, these results provide guidelines for the development of estrus-inducing protocols with other GnRH-agonists of known biopotencies.     

Increase of thyrotropin response to thyrotropin-releasing hormone (TRH) and TRH release in rats during pregnancy

Regulation of thyrotropin (TSH) release by thyrotropin releasing hormone (TRH) in the anterior pituitary gland (AP) of pregnant rats was studied. The pregnant (day 7, 14, and 21) and diestrous rats were decapitated. AP was divided into 2 halves, and then incubated with Locke's solution at 37 degrees C for 30 min following a preincubation. After replacing with media, APs were incubated with Locke's solution containing 0, or 10 nM TRH for 30 min. Both basal and TRH-stimulated media were collected at the end of incubation. Medial basal hypothalamus (MBH) was incubated with Locke's medium at 37 degrees C for 30 min. Concentrations of TSH in medium and plasma samples as well as the cyclic 3':5' adenosine monophosphate (cAMP) content in APs and the levels of TRH in MBH medium were measured by radioimmunoassay. The levels of plasma TSH were higher in pregnant rats of day 21 than in diestrous rats. The spontaneous release of TSH in vitro was unaltered by pregnancy. TRH increased the release of TSH by AP, which was higher in pregnant than in diestrous rats. Maternal serum concentration of total T3 was decreased during the pregnancy. The basal release of hypothalamic TRH in vitro was greater in late pregnant rats than in diestrous rats. After TRH stimulation, the increase of the content of pituitary cAMP was greater in late pregnant rats than in diestrus animals. These results suggest that the greater secretion of TSH in pregnant rats is in part due to an increase of spontaneous release of TRH by MBH and a decrease of plasma thyroid hormones. Moreover, the higher level of plasma TSH in rats during late pregnancy is associated with the greater response of pituitary cAMP and TSH to TRH.     

Adrenal cortical response in clinically normal dogs before and after adaptation to a housing environment

58 dogs (29 males and 29 females) selected as healthy on clinical and biochemical evaluations were subjected to an ACTH adrenal function test 2 days after their admission to a veterinary hospital (t + 0). Basal female serum cortisol concentrations were significantly higher than concentrations in males (77 nmol/l versus 43 nmol/l; P less than 0.01). Concentrations post stimulation were not statistically different (P greater than 0.05) between males and females: 306 (+/- 69) nmol/l versus 291 (+/- 73) nmol/l, respectively. Twelve dogs (6 males and 6 females), randomly selected from the 58, were subjected to the same test 5 weeks later (t + 5) and 12 weeks later (t + 12). Basal cortisol concentrations were lower at t + 5 or at t + 12 than at t + 0. Post stimulation mean cortisol concentrations were lower in males than in females at t + 5 (162 versus 232 nmol/l; P less than 0.05) but not at t + 0 (262 versus 320 nmol/l; P greater than 0.05) and t + 12 (188 versus 233 nmol/l; P greater than 0.05). These findings are indicating an increased susceptibility of bitches to environmental stress.     

Increased LH pulse frequency and estrogen secretion associated with termination of anestrus followed by enhancement of uterine estrogen receptor gene expression in the beagle bitch

The relationships among pulsatile LH secretion pattern, estrogen secretion, and expression of the uterine estrogen receptor gene were examined throughout the estrous cycle in beagle bitches. In Experiment 1, blood samples were collected from 30 bitches every 10 min for 8 h from a cephalic vein during different phases of the estrous cycle. An increase in the mean plasma levels of LH occurred from mid to late anestrus (P < 0.01). The LH pulse frequency increased (P < 0.01) from late anestrus to proestrus, and was strongly correlated (r = 0.96, P < 0.001) with the mean plasma level of estradiol-17 beta (E2). In Experiment 2, middle uterine samples, including the myometrium and endometrium, from 18 bitches were taken at 6 stages of the estrous cycle. The total number of estrogen receptors and nuclear estrogen receptor and its mRNA levels in the uterus also increased (P < 0.01) from late anestrus to proestrus. Mean plasma E2 level and the number of uterine estrogen receptor were positively correlated (r = 0.81, P < 0.05). In Experiment 3, nine bitches were ovariectomized in mid anestrus. Two weeks later they received a single injection of 10 or 50 micrograms/kg, i.m., estradiol benzoate. The number of uterine estrogen receptor and their mRNA levels for ovariectomized bitches were low, but increased (P < 0.05) after treatment with a low dose of estradiol benzoate. These results suggest that increases in LH pulse frequency and estrogen secretion are associated with termination of anestrus and that subsequent enhancement of uterine estrogen receptor expression may be up-regulated by estradiol.     

Pregnancy-specific elevations in fecal concentrations of estradiol, testosterone and progesterone in the domestic dog (Canis familiaris)

Estradiol (E2), testosterone (T) and progesterone (P4) concentrations were determined by enzyme-immunoassay in aqueous extracts of fecal samples obtained during anestrus, proestrus, estrus and metestrus of 11 nonpregnant and 11 pregnant bitches. Fecal hormone concentrations (ng/g) changed in relation to stage of cycle. Mean fecal steroid concentrations in 22 anestrous bitches and 3 ovariectomized bitches were low and similar for E2 (53 +/- 5 and 27 +/- 2), T (60 +/- 7 and 36 +/- 6), and P4 (62 +/- 6 and 86 +/- 15). Within 0 to 3 d of the ovulatory LH surge fecal E2 reached peak concentrations (301 +/- 38). The T peaks (281 +/- 41) were coincident or 1 to 3 d later. Fecal P4 was then elevated for approximately 2 m.o. Between Days 26 and 45 after ovulation, mean fecal P4 concentrations were higher (P < 0.05) in pregnant (401 +/- 60) than in nonpregnant bitches (164 +/- 23) and peak fecal P4 concentrations in individual animals were higher (P < 0.01) in pregnant (812 +/- 121) than in nonpregnant bitches (425 +/- 97). In the same period mean concentrations of E2 (117 +/- 13 vs 61 +/- 5) and T (102 +/- 10 vs 70 +/- 6) were also higher (P < or = 0.05) in pregnant than in nonpregnant bitches. Serum E2, T and P4 concentration were positively correlated (P = 0.1) with concentration in fecal samples obtained one day after serum collection. Although serial fecal ovarian steroid concentrations demonstrate the time course of ovulatory cycles, the diagnostic value of individual fecal samples appears limited. The ratios of peak to basal values were approximately 6, 5 and 7 for E2, T and P4, respectively, and were considerably lower than ratios of 12 to 50 previously reported for serum or plasma concentrations. The results demonstrate that there are pregnancy-specific increases in P4, E2 and T production reflected in fecal concentrations. While such increases are reflected in fecal samples, they are generally not evident in serum or plasma concentrations because of increased hemodilution, metabolism and clearance in pregnant bitches. The physiological stimulus for these increases, presumably ovarian in origin, or the potential role of prolactin is not known.     

Effects of canine serum collected from dogs at different estrous cycle stages on in vitro nuclear maturation of canine oocytes

Canine oocytes are ovulated at prophase of the first meiotic division and undergo maturation in the distal part of the oviduct for at least 48-72 h. Because of these differences from other domestic mammals, the efficiency of in vitro maturation (IVM) of canine oocyte is very low. The present study was conducted to evaluate the effects of canine serum on IVM of canine oocytes recovered from ovaries in various reproductive states (follicular, luteal or anestrous stages). Oocytes were recovered by mincing ovaries from bitches presented for ovariohysterectomy at various stages of the estrous cycle. Heat-inactivated canine serum was prepared with blood taken from dogs at the anestrous, estrous or diestrous stage of the estrous cycle as determined by progesterone concentration and vaginal cytology. Oocytes were cultured for 72 h in tissue culture medium (TCM)-199 supplemented with 10% canine anestrous, estrous or diestrous serum or fetal bovine serum (FBS) (experiment 1), or supplemented with 0 (control), 5%, 10% or 20% canine estrous serum (experiment 2). In experiment 1, IVM of oocytes collected at the follicular stage of the estrous cycle to metaphase II (MII) stage was higher (p < 0.05) with canine estrous serum (14.2%) than with canine anestrous (5.2%) or diestrous serum (6.3%), FBS (2.2%) or in the control (2.2%). In experiment 2, oocytes collected at the follicular stage of the estrous cycle cultured in TCM-199 with 10% canine estrous serum showed a higher maturation rate to MII stage (13.5%, p < 0.05) compared with those cultured with 5% (1.3% MII) or 20% canine estrous serum (5.1% MII) or the control (2.7% MII). In conclusion, our results demonstrate that supplementing culture medium with 10% canine estrous serum improves IVM of canine follicular stage oocytes.     

Influence of reproductive status on in vitro oocyte maturation in dogs

In the bitch, oocytes need 48-72 h to complete post-ovulatory maturation to the metaphase II stage in the isthmus of the oviduct, an interval similar to that found in in vitro studies. The effect of estrous cycle stage on in vitro meiotic competence of dog oocytes has been described in several studies. However, there are no reports evaluating the possible effects of pyometra or pregnancy on subsequent potential of oocytes recovered from such females to undergo in vitro maturation.In this study, immature cumulus-oocyte complexes (COCs) were recovered from fresh excised domestic dog ovaries in various reproductive states. The donor females were classified into groups based on stage of the estrous cycle: follicular (proestrus or estrus), luteal (diestrus) or anestrus or at the clinical conditions of pregnancy and pyometra. Grades 1 and 2 oocytes were cultured in vitro at 37 degrees C in TCM-199, supplemented with 25 mM Hepes/l (v/v), and with 10% heat inactived estrous cow serum (ECS), 50 microg/ml gentamicin, 2.2 mg/ml sodium carbonate, 22 microg/ml pyruvic acid, 1.0 microg/ml estradiol, 0.5 microg/ml FSH and 0.03 IU/ml hCG. The nuclear maturation rate was evaluated at 72 h of incubation under Hoechst 33342 (10 microg/ml) staining for fluorescence microscopy. There was no statistical difference in nuclear progression to the MII stage among the various reproductive states (follicular phase, 5.4%; diestrus, 4.2%; anestrus, 4.4%; pyometra, 8.1% and pregnancy, 4.7%). Resumption of meiosis was 24.6% at the follicular phase, 19.6% for diestrus, 16.4% for anestrus, 37.1% for pyometra and 29.2% for pregnancy. Positive and higher numbers of residue above the expected value were observed for the pyometra and pregnancy conditions at the metaphase/anaphase I (MI/AI) stages.Our results indicate that in vitro nuclear maturation of dogs oocytes is not influenced by the in vivo reproductive status of the female. The quality of the oocyte is a more reliable indicator of its potential for meiotic maturation in vitro than the hormonal environment of the donor female at the time of oocyte retrieval.     

Plasma thyroxine and cortisol under basal conditions and during cold stress in the aging dog

The effects of aging on plasma concentration of thyroxine (T4) and cortisol and on responses of these hormones to low ambient temperatures were determined in the dog. Female beagle dogs were divided into three age groups: old, adult, and puppies. The mean (+/- SD) ages were 11.4 +/- 0.2 years, 3.0 +/- 0.4 years, and 7.6 +/- 0.2 weeks, respectively. All dogs came from a genetically homogeneous colony and were free from any disease. The adult and old dogs were used during anestrus. Based on four daily blood samples, the mean (+/- SE) T4 level in the old dogs (2.8 +/- 0.1 microgram/dl) was significantly (P less than 0.001) lower than that in the adults (4.2 +/- 0.2 micrograms/dl) and puppies (4.4 +/- 0.2 micrograms/dl). By contrast, mean plasma cortisol levels in the old dogs (21.1 +/- 3.1 ng/ml) and adults (15.4 +/- 2.4 ng/ml) were significantly higher than those in the puppies (7.2 +/- 1.1 ng/ml). No significant changes in plasma T4 and cortisol occurred in any of the three age groups at 22 degrees C or during exposure to 10 or 4 degrees C. Exposure to -5 degrees C, however, produced significant increases in T4 (greater than 130% by 5 hr) and cortisol (greater than 280% by 1 hr) in adult dogs. This temperature produced only a modest increase in T4 (70% by 3.5 hr) and no change in cortisol in the old dogs. The puppies showed no change in T4 and cortisol during exposure to -5 degrees C. The results demonstrate that with advancing age, plasma T4 and cortisol concentrations change in opposite directions, thus supporting the hypothesis of a negative relationship between these two hormones. These results also show that the responses of these hormones to the stress of cold decline during aging and are not yet developed in the very young.     

Heterogeneity of circulating prolactin in the bitch

Different molecular forms of circulating prolactin (PRL) are known to occur in several species. As no such information was available in dogs, we assessed the molecular profile of circulating PRL in bitches. Pooled sera from covertly (CTRL) and overtly pseudopregnant (PSPT) diestrous bitches with high or low (> 10 or < 10 ng x mL(-1), respectively) serum PRL (measured by ELISA) were analyzed by Sephadex G-100 and Concanavalin A-Sepharose column chromatography. Four serum PRL fractions were identified and termed big-big, big (> 67 kDa), native (23 kDa) and fragmented (< 20) kDa) PRL. The percentages of these fractions were roughly similar in CTRL and PSPT animals, irrespective of their serum PRL levels (higher in PSPT than in CTRL bitches). A large proportion of glycosylated PRL (between 69 and 100%) was also detected in these sera. We conclude that in dogs, circulating PRL occurs in multiple molecular forms, whose relative abundance is comparable in covertly and overtly pseudopregnant bitches.     

Estrus induction in the bitch using a combination diethylstilbestrol and FSH-P

The purpose of the study was to induce estrus and ovulation in normal bitches using a combination of diethylstilbestrol (DES) and follicle stimulating hormone of porcine pituitary origin (FSH-P). Thirteen mature mongrel female dogs were divided into two groups, the first group was treated for estrus induction during late anestrus and the second group during mid-anestrus. The dogs were monitored by teasing, vaginal cytology, and hormonal assay during the induced (n = 13) and the previous spontaneous estrous cycle (n = 9). Six of eight and three of five bitches came into standing estrus in the first and second group, respectively. Of the bitches that came into estrus, three conceived in the first group and one in the second. The average induced litter size was 7.0 versus 7.5 for the colony. Based on vaginal cytology the induced proestrus and estrus lasted 1.7 (0 to 3) and 12.9 (4 to 24) d, respectively, while the spontaneous proestrus and estrus lasted 5.8 (0-17) and 12.8 (9-15) d, respectively. Progesterone profiles were similar between the induced and spontaneous estrous cycles, although the progesterone peak was higher during the spontaneous cycle. The preovulatory luteinizing hormone (LH) surge was observed in only one induced estrous cycle. Modest results were obtained with this therapy. However, the litter sizes were normal and the induced cycles were very similar to the physiologic ones. No side effects were seen with the oral form of DES.     

Chemical inhibition of estrus in the beagle

Twenty anestrus bitches were dosed orally for 90 days with vehicle or 0.9 mg/kg b.w. of 6,6-spiroethylene-19-nor-spiroxenone. All dogs were due in estrus during the test period based on previous average estrous cycle lengths. Estrus was prevented in 100% of the drug-treated bitches. Eight of ten control dogs came into heat during the test period. Hematological and blood biochemical studies did not show any consistent drug-related anomalies. Uterine biopsies, taken at laparotomy from half the dogs in each group, showed no evidence of cystic endometrial hyperplasia or pyometra. Mammary biopsies were also normal. Functional corpora lutea were observed in two control dogs at laparotomy. These dogs had high serum progesterone levels and a secretory endometrium. Drug-treated dogs had low serum progesterone levels and quiescent ovaries.     

Reproductive cycles of the domestic bitch

Domestic dogs are monoestrous, typically non-seasonal, polytocous, spontaneous ovulators and have a spontaneous luteal phase slightly longer (by approx 5 day) than the 64±1day luteal phases of a 65±1day pregnancy, a phase followed by an obligate anestrus before the next 2-3 week "heat" (proestrus-estrus). The resulting inter-estrus intervals of 5-12 months are variable among bitches, commonly 6-7 months, and range from highly variable to regular (to perhaps within±5-10 day of sequential 7 month cycle, for instance) within bitches, and across studies and do not vary significantly between pregnant and non-pregnant cycles. Hormone levels reported are those observed in this laboratory using previously reported assays and canine gonadotropin standards unless stated otherwise. Endocrine sequences for dog cycles are not unlike those of many other mammals, including selection of ovulatory follicles by increased LH pulsatility, the occurrence of estrus behavior and LH surge during a decline in the estrogen: progestin ratio, a pronounced preovulatory luteinization as in humans and rodents, and luteotrophic roles for both LH and prolactin. Non-pregnant bitches have a spontaneously prolonged luteal phase, often longer and with a more protracted decline in serum progesterone than in pregnancy as there is no uterine luteolytic mechanism. The obligate anestrus of 8-40 weeks is terminated by poorly understood interactions of environment (e.g. pheromones, possibly photoperiod) and a potential endogenous circannual cycle in sensitivities of hypothalamic dopaminergic, serotonergic and/or opioid pathways.     

Hormonal changes in spontaneous and aglépristone-induced parturition in dogs

To increase our understanding of the endocrine changes associated with parturition in dogs, plasma concentrations of progesterone (P4), 15-ketodihydroprostaglandin F(2alpha) (PGFM), estradiol-17-beta (E2beta), cortisol, ACTH, prolactin (PRL), LH, and FSH were measured in six spontaneously whelping bitches and in six bitches in which parturition was induced with the progesterone-receptor blocker aglépristone on day 58 of pregnancy. Expulsion of pups in the induced group took place in the presence of P4 concentrations that were still elevated. PGFM concentrations increased before parturition in both groups, but levels were lower in the induced bitches. PGFM levels reached a maximum in both groups during parturition and quickly decreased in the spontaneously whelping group after parturition, but remained elevated in the induced group. In both groups, cortisol concentrations reached similar maximum levels during the last 30 h before the onset of expulsion. During the 3 days postpartum, cortisol concentrations were higher in the induced group. The highly variable ACTH concentrations did not differ significantly throughout the study within or between groups. In both groups, E2beta concentrations decreased and PRL concentrations increased between the late gestational period and the 30-h period before parturition. Concentrations of both LH (spontaneously whelping group) and FSH (both groups) decreased between late gestation and the postpartum period. The results of this study illustrate the hormonal changes around parturition in the bitch, and reveal that aglépristone-induced parturition is associated with still incomplete luteolysis, an altered PGFM profile, and elevated postpartum cortisol concentrations as compared with spontaneously whelping dogs.     

Contact of dog spermatozoa with homologous uterine tube epithelium prolongs flagellar activity in relation to the stage of the estrous cycle

There is scant information about the storage of spermatozoa within the reproductive tract of the bitch. In several species the uterine tube plays a significant role in sperm storage. The present study was performed to investigate the interaction between spermatozoa and the epithelium of the uterine tube, in particular how this interaction might influence the flagellar activity of spermatozoa in relation to the stage of the estrous cycle. Epithelium was harvested from uterine tubes of 24 bitches at various stages of the estrous cycle (estrus, luteal phase or anestrus), and cultured with pooled spermatozoa collected from 6 dogs. Spermatozoa rapidly bound to the epithelial surface by their heads and the majority of attached spermatozoa were motile. The intimate association between spermatozoa and the uterine tube epithelium maintained motility in a manner that was related to the stage of the estrous cycle. Flagellar activity was significantly greater for spermatozoa bound to estrous epithelium than epithelium from the luteal phase or anestrus. On average, approximately 10% of spermatozoa that were attached to the uterine tube epithelium of estrous bitches retained their flagellar activity for 48 h after innoculation. There was no apparent influence of the region of the uterine tube on this effect. These findings suggest that the uterine tube may form a functional spermatozoal reservoir in the bitch.     

Insulin-like growth factor I (somatomedin C) in goats during normal lactation and in response to somatotropin treatment

1. Two experiments were performed. In Experiment 1, IGF-I concentrations in serum were followed in four lactating dairy goats during normal lactation and before, during and after 14 days of daily administration of 10 IU recombinant bovine somatotropin, starting 10 weeks post-partum. In Experiment 2, IGF-I was measured in single blood samples obtained from 40 dairy goats in the first part of lactation. 2. Measured IGF-I concentrations ranged from 4.4-9.0 nM. Concentrations varied during the day with coefficients of variation from 8.9 to 18.4% in the four goats in Experiment 1. There were no systematic trends in the diurnal variations (P greater than 0.75). 3. Concentrations of IGF-I remained fairly constant in all goats in Experiment 1 during the lactational period, and were not related to the changes in milk yield (P greater than 0.65). Similarly, no relationship was found in Experiment 2 between level of milk production and IGF-I concentration in serum. 4. Somatotropin treatment stimulated milk yields by 14 +/- 2.9% (P less than 0.05) and IGF-I concentration by 27.9 +/- 6.7% (P less than 0.05). 5. IGF-I is the most likely factor which increases mammary gland synthetic capacity in response to somatotropin treatment, and thus is responsible for the galactopoietic effect of this hormone being exerted. 6. However, serum IGF-I may primarily be involved in regulation of nutrient partitioning during normal lactation, but a paracrine synthesis with local effect on the mammary gland cannot be ruled out.     

Hormonal concentrations in bitches with primary uterine inertia

Normal labor is accompanied by sequential changes in blood concentrations of prostaglandin F2α (measured as 15-ketodihydro-PGF2α = PGFM), progesterone, estradiol, oxytocin, vasopressin, and of elevated cortisol levels. The aim of this study was to investigate hormone concentrations in dogs diagnosed with primary uterine inertia before and during treatment by cesarian section. The hypothesis was the dogs would have abnormally low plasma concentrations in one or several of the hormones involved in parturition. The study comprised seven bitches with total primary uterine inertia (dystocia group) treated with cesarian section and six healthy bitches (control group) subjected to planned cesarean section. Blood samples were taken before anesthesia, before surgery started, on delivery of the first puppy and on delivery of the last puppy. The progesterone:PGFM ratio in plasma was higher in the dystocia group than in the control group, but the serum estradiol concentration did not differ between groups. The plasma concentrations of oxytocin and vasopressin increased in both groups when the first puppies were delivered, but both hormones were more elevated in the control group than in the dystocia group on delivery of the last puppies. The plasma cortisol concentration increased to the same level in both groups. In conclusion, the ratio between progesterone and PGFM was higher and the oxytocin and vasopressin concentrations lower in the dystocia dogs than in the control dogs. The findings indicate that these hormones are involved in the pathophysiology of total primary uterine inertia in bitches.