The effects of maternal undernutrition on maternal and fetal serum insulin-like growth factors, thyroid hormones and cortisol in the guinea pig.

The insulin-like growth factors (IGF-I and -II) are potential mediators of the effects of maternal undernutrition on fetal growth and muscle development. The effects of a 40% reduction in maternal feed intake on serum levels of the IGFs, the thyroid hormones and cortisol, were investigated for the last two trimesters (day 25 to birth). This level of undernutrition is known to cause a 35% reduction in fetal and placental weights, and a 20-25% reduction in muscle fibre number. Maternal IGF-I level was greater than non-pregnant levels on day 25 gestation, in both control and restricted dams, and declined with gestational age. The increase in IGF-I level in the 40% restricted group was approximately two-thirds that of control animals. Fetal serum IGF-I was also reduced in undernourished fetuses throughout gestation. Maternal IGF-II did not change with gestational age and was unaffected by undernutrition. Fetal IGF-II reached a peak at day 55 of gestation, this peak was greatly diminished by maternal feed restriction. Both IGF-I and IGF-II tended to be related to fetal, placental and muscle weights at day 65 of gestation. Thyroid hormone concentration declined in maternal serum and increased in fetal serum with increasing gestational age. Levels were not significantly affected by undernutrition. Both triiodothyronine (T3) and thyroxine (T4) were correlated with IGF-I in maternal serum (P < 0.05), but not in fetal serum. Cortisol levels were elevated by undernutrition in both maternal and fetal serum, and increased with gestational age. Cortisol was inversely correlated with serum IGF-I in both maternal and fetal serum. Maternal serum IGF-I may mediate the effects of undernutrition on fetal growth by affecting the growth and establishment of the feto-placental unit in mid-gestation. Fetal IGF-I may mediate the effects on muscle growth, whereas IGF-II seems to be related to hepatic glycogen deposition. Cortisol may play a role via its effect on the IGFs, but the thyroid hormones are unlikely to be important until the late gestation/early postnatal period.     

Placental transfer of cholesterol-4-14C into rabbit and guinea pig fetus

A tracer dose of cholesterol-4-(14)C was given daily in the diet of six pregnant guinea pigs to establish an isotopic steady state. At the time of parturition, maternal and fetal blood and fetal tissues were collected and analyzed for cholesterol content and cholesterol specific activity. A comparison of these specific activities in neonatal and maternal serum indicated that about 22% of the fetal serum cholesterol was transferred from maternal blood. In the newborn, tissues generally had the same cholesterol specific activity as serum. Brain tissue was an exception in having a specific activity only 8.4% of that of serum. Dietary cholesterol did not increase serum cholesterol levels in the newborn but did increase the percentage of fetal cholesterol derived from the maternal circulation. The rapid transfer of cholesterol-4-(14)C across the placenta was indicated by the appearance of this isotope in the newborn 2 days after its administration to pregnant rabbits. A considerable amount of the cholesterol content of newborn guinea pigs and rabbits originated from the maternal blood.     

Plasma levels of 16 alpha-hydroxypregnenolone, 16 alpha-hydroxyprogesterone and 16 alpha-hydroxydehydroepiandrosterone in the fetus and neonates.

Simultaneous determination of unconjugated 16 alpha-hydroxypregnenolone (16 alphaOH-Preg), 16 alpha-hydroxyprogesterone (16 alphaOH-Prog) and 16 alpha-hydroxydehydroepiandrosterone (16 alphaOH-DHEA) in fetal and neonatal plasma was performed utilizing a newly developed radioimmunoassay. In all neonates, the three 16 alpha-hydroxysteroid levels were consistently higher in umbilical cord plasma than in the maternal peripheral circulation. 16 alpha-OH-Preg in the umbilical arterial plasma increased from 11.2 +/- 3.1 at 24 weeks to 29.7 +/- 12.0 ng/ml at term, 16 alphaOH-Prog from 15.5 +/- 3.2 to 34.3 +/- 11.0 ng/ml and 16 alphaOH-DHEA from 5.1 +/- 1.2 to 5.9 +/- 1.0 ng/ml. In the anencephalic neonates, only 16 alphaOH-Preg showed an increase pattern under ACTH priming. 16 alpha-OH-Preg levels for normal full term neonates remain relatively constant at the first 24 hr and show a slight decrease at 3 days post partum. In small full term neonates, 16 alphaOH-Preg levels in umbilical arterial plasma are considerably higher than in normal neonates and remain at roughly equivalent levels for the first 5 days post partum. 16 alphaOH-Prog and 16 alphaOH-DHEA levels in umbilical arterial plasma in normal and small full term neonates are almost equal and both groups show a rapid decrease during the first 24 hr. Comparison with findings of the three 16 alpha-hydroxysteroids in fetal and neonatal plasma is discussed.     

Changes in fetal and maternal blood levels of prolactin, cortisol, and cortisone during eutocic and dystocic childbirth

The changes in blood levels of prolactin, total and free cortisol, and cortisone were studied and compared in 51 mother-infant pairs, 30 with eutocic delivery and 21 with dystocic delivery. Regardless of the type of delivery, the newborn at term showed significantly higher prolactin and cortisone serum levels than their mothers, and significantly lower levels of free and total cortisol. In fetal distress of short duration, free cortisol levels were significantly raised in both the mother and the child, while prolactin and cortisone levels were significantly higher only in the child. In contrast to these observations, serum prolactin and cortisone levels in the mother were not altered by the occurrence of fetal distress. In the newborn at delivery there was a negative correlation between serum prolactin and the Apgar score at 1 min applied to the part of the graph between 8 and 2 Apgar scores. This study illustrates the utility of fetal prolactin measurements in evaluating the stress to which the fetus is subjected.     

Effects of acute and chronic trazodone administration on serum prolactin levels in adult female rats

Trazodone was tested for its ability to elevate serum prolactin levels in mature female rats. When the drug was administered acutely to female rats at doses up to 80 mg/kg ip, it induced a clear rise in serum prolactin levels, with a minimum effective dose of 20 mg/kg; blood trazodone levels at these doses were between 1.6–2.4 μg/ml. However, trazodone could not be considered to be a potent stimulator of prolactin secretion, since the injection of haloperidol at 2 mg/kg elevated serum prolactin to values twice those seen in animals receiving the 80 mg/kg dose of trazodone. When trazodone was administered chronically in the diet for two or four weeks, at an average daily dose of 80 mg/kg, serum trazodone levels were found to be 100–200 ng/ml when measured at each stage of the estrous cycle. Serum prolactin levels in trazodone-treated animals, however, did $\text{not}$ differ from those in control rats. Moreover, drug-treated animals showed normal proestrus surges in serum prolactin. The results of these studies thus indicate that acutely, at very high doses, trazodone probably can stimulate prolactin secretion modestly in female rats. However, when consumed chronically at 80 mg/kg/day, the drug has no effects on serum prolactin levels. Therefore, if trazodone stimulates prolactin secretion by altering neurotransmission across dopamine and/or serotonin synapses in brain, it is probably not potent in these actions, at least as concerns those dopamine and serotonin neurons that influence the secretion of prolactin.     

Prolactin inhibition in lactating rats changes leptin transfer through the milk.

Malnutrition during lactation reduces milk production and changes pup's leptin serum levels. To test prolactin role in this nutritional state, we evaluated whether prolactin suppression during lactation changes serum leptin in dams, its transfer through the milk, and pup's serum leptin. Lactating rats were treated with bromocryptine (1 mg/twice a day, s.c.) or saline three days before sacrifice (days 2-4 or days 19-21). Food intake and body weight were measured until sacrifice (4th and 21st day). Serum prolactin and leptin were determined by radioimmunoassay. Bromocryptine injected dams had lower serum prolactin and milk production as expected. The mothers presented lower food ingestion (day 21: -25%), lower body weight (day 4: -12%; day 21: -10%), higher serum leptin (day 4: +68%), lower milk leptin on the 4th day (11 times) and higher (8 times) on the 21st day. The offspring of bromocryptine-treated mothers presented lower body weight in both periods of lactation and lower serum leptin on the 4th day (-40%) and higher on the 21st day (+37%) of lactation. We suggest that prolactin, through its effect on leptin secretion into the milk, may play an important role in signalizing maternal nutritional status to the pups.     

Prostaglandin F and E levels in the conceptus, uterus and plasma during early pregnancy in the ewe

Concentrations of prostaglandins E and F (PGE and PGF) were measured in the embryo or fetus, extra embryonic or fetal membranes (membranes), intercaruncular and caruncular endometrium and plasma collected from uterine and ovarian arterial and venous vessels from separate groups of ewes laparotomized at 5 day intervals from day 10 to day 55 of pregnancy. Our purpose was to investigate the role of prostaglandins E and F in the maternal recognition of pregnancy, implantation and early placental function. Our data suggest that the initial maintenance of the corpus luteum in the pregnant ewe does not involve a reduction in PGF production, compared to pregnant ewes; but a change in the pattern of PGF secretion. This is accompanied by an elevation in PGE production of similar magnitude to that observed in non pregnant ewes. The extra embryonic/fetal membranes appear to be the major source of elevated PGF levels in the maternal circulation prior to day 30 of pregnancy. Between days 35 and 55 of gestation the rising PGF levels in maternal serum probably come from the fetus. Over the same period PGE levels rise in the fetus and intercaruncular endometrium, but PGE secretion into the maternal circulation is not enhanced. A role for PGF and PGE in fetal, placental and uterine growth is suggested; placental and uterine endocrine function may also be targets.     

Prostaglandin F and E levels in the conceptus, uterus and plasma during early pregnancy in the ewe

Concentrations of prostaglandins E and F (PGE and PGF) were measured in the embryo or fetus, extra embryonic or fetal membranes (membranes), intercaruncular and caruncular endometrium and plasma collected from uterine and ovarian arterial and venous vessels from separate groups of ewes laparotomized at 5 day intervals from day 10 to day 55 of pregnancy. Our purpose was to investigate the role of prostaglandins E and F in the maternal recognition of pregnancy, implantation and early placental function. Our data suggest that the initial maintenance of the corpus luteum in the pregnant ewe does not involve a reduction in PGF production, compared to pregnant ewes; but a change in the pattern of PGF secretion. This is accompanied by an elevation in PGE production of similar magnitude to that observed in non pregnant ewes. The extra embryonic/fetal membranes appear to be the major source of elevated PGF levels in the maternal circulation prior to day 30 of pregnancy. Between days 35 and 55 of gestation the rising PGF levels in maternal serum probably come from the fetus. Over the same period PGE levels rise in the fetus and intercaruncular endometrium, but PGE secretion into the maternal circulation is not enhanced. A role for PGF and PGE in fetal, placental and uterine growth is suggested; placental and uterine endocrine function may also be targets.     

Maternal hypoxia alters matrix metalloproteinase expression patterns and causes cardiac remodeling in fetal and neonatal rats

Fetal hypoxia leads to progressive cardiac remodeling in rat offspring. The present study tested the hypothesis that maternal hypoxia results in reprogramming of matrix metalloproteinase (MMP) expression patterns and fibrillar collagen matrix in the developing heart. Pregnant rats were treated with normoxia or hypoxia (10.5% O(2)) from day 15 to 21 of gestation. Hearts were isolated from 21-day fetuses (E21) and postnatal day 7 pups (PD7). Maternal hypoxia caused a decrease in the body weight of both E21 and PD7. The heart-to-body weight ratio was increased in E21 but not in PD7. Left ventricular myocardium wall thickness and cardiomyocyte proliferation were significantly decreased in both fetal and neonatal hearts. Hypoxia had no effect on fibrillar collagen content in the fetal heart, but significantly increased the collagen content in the neonatal heart. Western blotting revealed that maternal hypoxia significantly increased collagen I, but not collagen III, levels in the neonatal heart. Maternal hypoxia decreased MMP-1 but increased MMP-13 and membrane type (MT)1-MMP in the fetal heart. In the neonatal heart, MMP-1 and MMP-13 were significantly increased. Active MMP-2 and MMP-9 levels and activities were not altered in either fetal or neonatal hearts. Hypoxia significantly increased tissue inhibitors of metalloproteinase (TIMP)-3 and TIMP-4 in both fetal and neonatal hearts. In contrast, TIMP-1 and TIMP-2 were not affected. The results demonstrate that in utero hypoxia reprograms the expression patterns of MMPs and TIMPs and causes cardiac tissue remodeling with the increased collagen deposition in the developing heart.     

Differential effects of photoperiodic history on the responses of gonadotrophins and prolactin to intermediate daylengths in the male Syrian hamster

The effect of photoperiodic history on the neuroendocrine response to intermediate daylengths (11-13.5 hr of light) was investigated in the male Syrian hamster. The duration of the nocturnal peak of pineal melatonin content was inversely proportional to photoperiod and independent of photoperiodic history. Serum levels of prolactin were lower in animals exposed to shorter photoperiods. Photoperiodic history had little effect on the response of serum prolactin to intermediate daylengths. Serum luteinizing hormone (LH) concentrations were also lower in shorter photoperiods, but in addition were sensitive to the direction of photoperiodic change, so that a single photoperiod could be interpreted as either stimulatory or inhibitory to LH secretion. This effect of photoperiodic history was expressed at intermediate photoperiods with 12-13.5 hr of light. The sensitivity of serum follicle-stimulating hormone (FSH) levels to photoperiodic history was masked by an early onset of photorefractoriness. Testicular size and serum testosterone levels revealed weaker effects of photoperiodic history; these were attributed to the dissociation between gonadotrophin and prolactin secretion induced by intermediate daylengths. The contrasting effects of photoperiodic history on the secretion of LH and prolactin may represent the expression of multiple photoperiodic time-measuring systems.     

Nutrition and fetal brain maturation : II. Impact of maternal starvation on changing levels of acetylcholinesterase and enolase in vitro

The impact of maternal starvation during Days 17-20 of gestation was examined in 20-day fetal rat brain tissue cultured for 6 days in MEM and 10% adult rat serum. Acetylcholinesterase (AChE) activities were consistently greater in fetal brain cell cultures from starved mothers. When fetal tissues from starved mothers were continuously exposed to 72-h fasted serum, AChE activities increased from 1.03 +/- 0.14 to 1.59 +/- 0.21 mumol/h/mg protein (P less than 0.001). In fetal tissues from fed mothers, lower AChE activities were increased from 0.78 +/- 0.09 to 1.04 +/- 0.07 mumol/h/mg protein (P less than 0.05) when 72-h fasted serum was used to replace the fed serum during incubation. When fetal brain cell cultures from fed mothers were exposed for 6 days to graded concentrations of fed serum (2.5-15%), the activities of AChE fell reciprocally from 1.34 +/- 0.10 to 0.82 +/- 0.12 mumol/h/mg protein (P less than 0.05). The levels of AChE activity in tissues exposed to fasted serum were consistently greater, but fell similarly from 1.62 +/- 0.10 to 0.97 +/- 14 mumol/h/mg protein (P less than 0.01), when serum concentrations were increased from 2.5 to 15%. AChE activities were 30% higher in tissues incubated with cycloheximide 10(-3) M (P less than 0.02). Unlike AChE, fetal brain enolase activities were unaffected by maternal starvation. In fetal brain cell cultures from fed mothers, enolase fell from 1.85 +/- 0.10 to 1.37 +/- 0.12 mumol/min/mg protein following exposure to fasted instead of fed serum (P less than 0.02). In fetal cultures from starved mothers, enolase activities were depressed similarly from 1.76 +/- 0.08 to 1.41 +/- 0.09 mumol/min/mg protein when fasted replaced fed serum (P less than 0.02). Thus, the fetal brain cell cultures appear to maintain enzymatic realignments imposed by maternal starvation for at least 6 days. In addition, serum from fasted animals has significant growth inhibiting properties manifested by heightened activities of AChE and lower activities of enolase.     

Distinct expression of midkine and pleiotrophin in the spinal cord and placental tissues during early mouse development

Midkine and pleiotrophin comprise a family of heparin-binding growth factors, and are expressed in overlapping tissues during the mid- to late-gestation periods of mouse development. Their distinct expression during early mouse development, as revealed by in situ hybridization, was reported. Midkine was expressed in the embryonic ectoderm from as early as embryonic day (E5.5). In the neural tube midkine was expressed specifically in the neuroepithelium, that is, in the whole area of the neural tube at E9.5, and in the ventricular zone from E10.5-13.5. At E15.5, when the neuroepithelium disappeared, midkine concomitantly became undetectable. In contrast, pleiotrophin expression started exclusively in the neural plate at E8.5, and in the lateral plate of the neural tube at E9.5. It then became restricted to a dorsal ventricular zone from E11.5-13.5, and finally to the central gray neurons at E15.5. Moreover, pleiotrophin was expressed in the ventral horns. Among placental tissues, midkine was detected in the chorion, the fetal component of the placenta, whereas pleiotrophin was found in the decidua basalis, the maternal component of the placenta. The distinct expression of midkine and pleiotrophin suggests their differential role in early development.     

Gestational profiles of rat placental lactogen-II (rPL-II) and growth hormone (GH) in maternal and fetal serum, amniotic fluid, and placental tissue.

Rat placental lactogen-II (rPL-II) and growth hormone (rGH) in maternal and fetal serum, amniotic fluid, and placental tissue were measured by a homologous radioimmunoassay during the last half of pregnancy. rPL-II appeared first in maternal circulation and the placental tissue on day 11 of pregnancy. The maternal serum rPL-II concentration increased progressively and reached the peak value (684 +/- 76 ng/ml) on day 19, and declined thereafter up to term. rPL-II content in the tissue had a similar pattern to the maternal serum profile of rPL-II, while its concentration in the tissue increased dramatically on day 12 and remained high until day 19. Fetal serum rPL-II was detected on days 17 and 18, though its concentration was much lower (ranged between 3-10 ng/ml) than that of maternal serum. rPL-II in amniotic fluid was also detectable only on days 12-14 of pregnancy, and the peak value on day 13 was 22% of the maternal serum rPL-II concentration. The rGH concentration increased gradually as pregnancy advanced with a decline on the day before parturition. Although rGH in fetal serum increased on day 20 with a decline on the following day, it was slightly detectable in amniotic fluid on the last two days of pregnancy. The molecular profile of rPL-II in amniotic fluid and maternal serum of day 13 pregnant rats were examined by Western blotting. Anti-rPL-II serum detected two proteins with molecular weights (mol wt) of 19.5K and 20.5K in amniotic fluid and one protein with a mol wt of 20.5K in maternal serum under nonreducing conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transplacental transport of alpha 2-macroglobulin (alpha 2M) and induction of alpha 2M in maternal and neonatal rats with acute inflammation.

The aims of this study were to investigate transplacental transport of alpha 2-macroglobulin (alpha 2M) in rats in rats and to examine the degree of alpha 2M induction in maternal and neonatal rats with acute inflammation. Serum was collected from healthy pregnant CD (IGS) rats, neonates of the pregnant rats and their cord blood. Additional serum samples were obtained from pregnant rats inoculated with an inflammatory agent, turpentine oil, their neonates and cord blood, and neonates inoculated with turpentine oil. The serum levels of alpha 2M were measured by means of an enzyme-linked immunosorbent assay. The average serum levels of alpha 2M in healthy neonates and cord blood were about 380 micrograms/ml. Serum a2M level in neonates inoculated with turpentine oil averaged about 580 micrograms/ml. Serum alpha 2M levels in maternal rats inoculated with turpentine oil, neonates from those rats and their cord blood were elevated, the values being 2,000 micrograms/ml or higher. It was demonstrated that induction of alpha 2M in neonatal rats was lower than in maternal rats when inoculated with turpentine oil. These results suggest that alpha 2M is transplacentally transported from maternal rats to fetal ones.     

Effect of hyperthermia on the plasma concentrations of prolactin and cortisol in the fetal lamb and pregnant ewe during late gestation

Exposing pregnant sheep to an ambient temperature of 43 +/- 1 degree C for 8 h was associated with a 1-1.5 degrees C increase of maternal and fetal core temperatures, and a 11-fold and 3-5 fold increase in maternal and fetal plasma prolactin concentrations respectively. Hyperthermia did not change maternal or fetal plasma cortisol concentrations. We conclude that maternal and fetal hyperprolactinaemia may occur in late pregnancy during hyperthermic conditions and that the increase in fetal plasma prolactin is due to either increased secretion or decreased metabolic clearance of prolactin in the feto-placental compartment.     

The relationship between serum prolactin levels and disease activity in patients with Behcet's disease

The aim of this study was to determine the serum levels of prolactin in patients with Behcet's disease and to evaluate its correlation with disease activity. Serum prolactin levels were measured by a chemiluminescence method in 32 patients with Behcet's disease and compared with 20 age-and sex-matched healthy controls. The patients with Behcet's disease were subdivided into two groups according to disease activity: active (18 patients; 13 men and five women, average age 34.0 +/- 6.5 (28-48) years), and inactive (14 patients; 10 men and four women, average age 32.7 +/- 3.1 (22-49 years). Patients with active Behcet's disease had higher serum prolactin levels than the inactive and control groups. Prolactin levels in patients with active Behcet's disease differed significantly from the healthy control subjects (p < 0.05) only, but not the inactive group. Four patients out of 32 (12.5%) Behcet's disease patients showed mild hyperprolactinemia. All four of these cases were from the active Behcet's disease group. Prolactin levels were correlated with ESR (p < 0.05) and CRP (p < 0.05) levels in the active BD group, but not in the inactive BD and control groups. Our results suggest a possible role for this immunoregulatory hormone in the disease expression and pathogenesis of Behcet's disease.     

Rabbit corticosteroid-binding globulin: primary structure and biosynthesis during pregnancy

The cDNA-deduced primary structure of rabbit corticosteroid-binding globulin (CBG) contains 383 amino acids (mol wt, 42,326), including three cysteine residues and four sites for N-glycosylation. It is primarily the product of a 1.68-kilobase hepatic mRNA, but small amounts of CBG mRNA were also found in maternal lung, spleen, and ovary and fetal kidney. In the fetus, hepatic CBG mRNA concentrations increase markedly after day 11 and were 2- to 5-fold higher than those in maternal liver during days 17-23. They then declined to very low levels at term (31 days). By contrast, maternal hepatic CBG mRNA levels did not increase until day 23; reached a peak at about day 27, and then declined to prepregnancy values by 3 days after delivery. In general, fetal and maternal hepatic CBG mRNA concentrations reflect the corresponding serum CBG levels. Our data, therefore, indicate that the marked changes in fetal and maternal plasma CBG levels during pregnancy reflect changes in the biosynthesis of the protein rather than alterations in compartmentalization or clearance.     

Correlation between birth weight, leptin, zinc and copper levels in maternal and cord blood

Leptin and zinc are involved in the regulation of appetite. Copper is a trace element regulating the functions of several cuproenzymes that are essential for life. To evaluate the relationship between zinc and copper status and the leptin system in humans, we examined whether leptin concentrations in the mother and the newborn correlate with the weight of mother, placenta and newborn. A total of 88 pregnant women at 38-42 weeks' gestation were studied. All infants were categorized as small for gestational age (SGA) (n = 16), average for gestational age (AGA) (n = 59) or large for gestational age (LGA) (n = 13). Leptin, zinc, and copper levels were measured in maternal and cord serum at birth. Maternal BMI and placental weight of the LGA groups were significantly higher than those of the SGA and AGA groups. Cord and maternal leptin levels of the SGA groups were significantly lower than those of the AGA and LGA groups. Maternal serum leptin levels were positively correlated with BMI and maternal zinc levels in all groups. Cord serum leptin levels of all groups were positively correlated with birth weight and placental weight. Birth weight was negatively correlated with maternal and cord copper level of all groups. Umbilical leptin concentrations of SGA newborns correlated with leptin concentrations of their mothers. In all pregnancies, birth weight increases in association with increase in cord leptin level. Our results suggest that maternal zinc but not copper level has an effect on maternal serum leptin levels. The increase in copper level in both maternal and cord blood may contribute to restriction in fetal growth.     

Hormonal regulation of the synthesis of casein and alpha-lactalbumin in a primary mammary cell culture system

The addition of 5 micrograms/ml of both insulin and prolactin, 3 microM cortisol and 5% fetal bovine serum stimulated casein synthesis during a 5 day culture of mammary epithelium from lactating mice using a floating collagen gel as a culture substratum. Omission of any of the three hormones or serum decreased casein synthesis substantially. The use of 10% serum or the attached gel culture system also decreased casein synthesis. Cells cultured with the combination of the three hormones and 5% serum contained a low level of casein mRNA on day 2, but it increased to much higher levels on day 4 and 5, amounting to over 30% of total mRNA on day 5. In contrast to casein synthesis, the maximal increase in alpha-lactalbumin synthesis required the presence of 0.03 microM cortisol. The combination of insulin, prolactin and 3 microM cortisol or insulin and prolactin elicited smaller increases. The translatable mRNA for alpha-lactalbumin in cells cultured with insulin, cortisol and prolactin for 5 days was detected, but not in cells with insulin and cortisol. Both a high and low concentration of cortisol in combination with insulin increased prolactin binding capacity of cultured cells to the same extent, whereas cells cultured with insulin alone contained much lower levels of prolactin binding. The difference in the capacity of prolactin binding between cells cultured with insulin alone and those cultured with insulin and cortisol correlated well with their ability to synthesize casein in response to prolactin.