Progesterone secretion by adrenal glands of hamsters and comparison of ACTH influence in rats and hamsters.

Studies were designed to determine a) if adrenal glands of hamsters secrete progesterone (PROG), b) the effects of adrenocritocotropin (ACTH) administration on adrenocortial function of rats and hamsters under the surgical conditions necessary for collection of adrenal venous blood from the left renal vein, and c) the effects of blood loss during sample collection. PROG was quantitated by the competitive protein-binding method after extraction and separation by sephadex LH-20 column chromatography. The presence of interfering quantities of androstenedione necessitated two column chromatographic steps. Glucocorticoids (11-OHCS) were determined fluorometrically. PROG was detected in adrenal venous plasma of female hamsters. The PROG concentration and secretory rate were 91 +/- 12 ng/ml and 4 +/- 1 ng/min, respectively, while the peripheral plasma level of the same animals was 2 +/- 0.2 ng/ml, indicating that the adrenal glands of female hamsters are capable of secreting PROG. ACTH administration increased PROG secretory rates in both hamsters (3 +/- 1 to 14 +/- 3 ng/min) and rats (62 +/- 9 to 152 +/- 32 ng/min) on estrus, as well as increasing the 11-OHCS secretory rate of hamsters (16 +/- 1 to 33 +/- 4 ng/min), but not of rats. The greater increase in PRCC than in 11-OHCS secretion may be related to excess PROG formation relative to the capacity of the 17alpha- or 21-hydroxylating enzyme systems. The adrenal venous PROG concentration and secretory rate of female hamsters infused with 10% dextran while collecting adrenal venous blood did not differ significantly from those of the non-infused animals, suggesting that this amount of blood loss (1 ml) does not influence PROG secretion.     

Adrenal contribution to circulating estrogens in woman.

To study the contribution of adrenal glands to circulating estrogens in woman, the concentrations of estrone (E1), estradiol-17 beta (E2), and estriol (E3) in adrenal and peripheral venous blood were measured by radioimmunoassay and the grandular secretion of estrogens after ACTH stimulation was investigated by analyzing the adrenal vein levels of these steroids in patients with breast cancer who were undergoing a therapeutic adrenal operation. Furthermore, adrenal secretion rates of estrogens and cortisol were estimated. It was shown that there existed greater concentrations of estrogens in adrenal vein than in peripheral blood; about 3 times higher for E1 (p less than 0.001), and 2 times higher for E2 and E3 (p less than 0.05). Administration of ACTH caused a significant increase of E1 and E2 concentrations in adrenal venous blood to mean 150% of the basal levels that was comparable to the increase of cortisol. Apparent adrenal secretion rates of estrogens estimated under surgical situation were calculated to be 7.7 +/- 1.7 (M +/- SE) microgram/day for E1, 1.9 +/- 0.3 microgram/day for E2, and 0.3 +/- 0.2 microgram/day for E3, while the secretion rate of cortisol was 52.7 +/- 8.2 microgram/min. The present study demonstrates that the direct adrenal secretion of not only E1, but E2 and E3 contributes to the circulating estrogen levels, and it is suggested that the adrenal glands might be responsible for the relatively important source of estrogen production in the aged woman.     

Functional involvement of angiotensin AT2 receptor in adrenal catecholamine secretion in vivo.

The aim of the present study was to analyse modulations of adrenal catecholamine secretion from the adrenal gland of anesthetized dogs in response to locally administered angiotensin II (AngII) in the presence of either PD 123319 or CGP 42112, both of which are highly specific and selective ligands to angiotensin AT2 receptor. Plasma concentrations of epinephrine and norepinephrine in adrenal venous and aortic blood were quantified by a high performance liquid chromatography coupled with electrochemical detection (HPLC-EC) method. Adrenal venous blood flow was measured by gravimetry. Local administration of AngII (0.05 microg, 0.1 microM) to the left adrenal gland increased adrenal gland catecholamine output more than 30 times that found in nonstimulated states. Administration of either PD 123319 (0.085 microg (0.23 microM) to 8.5 microg (23 microM)) or CGP 42112 (0.005 microg (0.01 microM) to 5 microg (10 microM)) did not affect the basal catecholamine output significantly. The increase in adrenal catecholamine output in response to AngII was inhibited by approximately 80% following the largest dose of PD 123319. CGP 42112 significantly attenuated the catecholamine response to AngII by approximately 70%. PD 123319 and CGP 42112 were devoid of any agonist actions with respect to catecholamine output by the adrenal gland in vivo. Furthermore, both PD 123319 and CGP 42112 inhibited the increase in adrenal catecholamine secretion induced by local administration of AngII. The present study suggests that AT2 receptors play a role in mediating catecholamine secretion by the adrenal medulla in response to AngII receptor agonist administration in vivo.     

Role of PAC(1) receptor in adrenal catecholamine secretion induced by PACAP and VIP in vivo

The present study was conducted to investigate the functional implication of the pituitary adenylate cyclase-activating polypeptide (PACAP) type I (PAC(1)) receptor in the adrenal catecholamine (CA) secretion induced by either PACAP-27 or vasoactive intestinal polypeptide (VIP) in anesthetized dogs. PACAP-27, VIP, and their respective antagonists were locally infused to the left adrenal gland via the left adrenolumbar artery. Plasma CA concentrations in adrenal venous and aortic blood were determined by means of a high-performance liquid chromatograph coupled with an electrochemical detector. Adrenal venous blood flow was measured by gravimetry. The administration of PACAP-27 (50 ng) resulted in a significant increase in adrenal CA output. VIP (5 microg) also increased the basal CA secretion to an extent comparable to that observed with PACAP-27. In the presence of PACAP partial sequence 6--27 [PACAP-(6--27); a PAC(1) receptor antagonist] at the doses of 7.5 and 15 microg, the CA response to PACAP-27 was attenuated by approximately 50 and approximately 95%, respectively. Although the CA secretagogue effect of VIP was blocked by approximately 85% in the presence of PACAP-(6--27) (15 microg), it remained unaffected by VIP partial sequence 10--28 [VIP-(10--28); a VIP receptor antagonist] at the dose of 15 microg. Furthermore, the CA response to PACAP-27 did not change in the presence of the same dose of VIP--(10--28). The results indicate that PACAP-(6--27) diminished, in a dose-dependent manner, the increase in adrenal CA secretion induced by PACAP-27. The results also indicate that the CA response to either PACAP-27 or VIP was selectively inhibited by PACAP-(6--27) but not by VIP-(10--28). It is concluded that PAC(1) receptor is primarily involved in the CA secretion induced by both PACAP-27 and VIP in the canine adrenal medulla in vivo.     

Hormonal control of uteroglobin secretion in rabbit uterus. Inhibition of uteroglobin synthesis and messenger ribonucleic acid accumulation by oestrogen and anti-oestrogen administration

Investigations were conducted to quantify activity of uteroglobin mRNA and secretion of uteroglobin in rabbit uterus after administration of progesterone and 5alpha-dihydrotestosterone, either alone or concomitantly with oestradiol-17beta and tamoxifen, a non-steroidal anti-oestrogen. Poly(A)-containing mRNA was isolated from the uterine tissue by extraction with phenol/chloroform, precipitation with ethanol and chromatography on oligo(dT)-cellulose. Cell-free translation in vitro of the poly(A)-containing mRNA was carried out in a wheat-germ lysate, and the product isolated by specific immuno-precipitation with anti-uteroglobin antiserum purified by affinity chromatography. Radioimmunoassay was utilized to determine uteroglobin content in the uterine flushings and tissue preparations. When given for 5 days, both progesterone (1mg/kg per day) and 5alpha-dihydrotestosterone (25mg/kg per day) elicited a marked induction of uteroglobin secretion, which was accompanied with accumulation of uteroglobin mRNA in the tissue. Concomitant administration of oestradiol-17beta (50mug/kg per day) or tamoxifen (12.5mg/kg per day) significantly decreased both progesterone- and 5alpha-dihydrotestosterone-induced uteroglobin secretion, with a parallel decrease in the uteroglobin-mRNA activity. The decline in the uteroglobin content of the uterine flushes brought about by oestradiol-17beta or tamoxifen administration was not due to inhibition of secretion of this protein by the endometrial cells, since a simultaneous decrease occurred in the tissue uteroglobin content. After a 5-day pretreatment with progesterone (1mg/kg per day), administration of oestradiol-17beta (50mug/kg per day) during the ensuing 4 days greatly accelerated the decay of the uteroglobin content in the uterine fluid.     

Platelet-activating factor alters the dynamics of prostaglandin and protein synthesis by endometrial explants from pregnant and cyclic cows at day 17 following estrus

Factors produced by bovine conceptuses alter prostaglandin (PG) and protein secretion by endometrial explants from cyclic cows and induce an intracellular inhibitor of PG synthesis. Endometrial explants from cyclic (n = 4) and pregnant (n = 3) cows at Day 17 following estrus were incubated for 24 h with 0, 0.1, 0.5, 1 and 5 mug platelet-activating factor (PAF)/ml. Cotyledonary microsomes from parturient cows were utilized to determine levels of an intracellular/cytosolic inhibitor of PG synthesis. Endometrial explants from additional cyclic cows (n = 4) were incubated for 24 h with 0 or 5 mug PAF/ml with and without 50 muCi [(3)H]leucine. Endometrial explants (cyclic cows, n = 3) were also incubated for 12 h with each of the following treatments: 1) Control; 2) PAF (1 mug/ml); 3) lyso-PAF (2 to 10 mug/ml); 4) PAF-receptor antagonist (2 to 10 mug/ml); 5) PAF (1 mug/ml) + antagonist (2 to 10 mug/ml); 6) bovine conceptus secretory proteins (bCSP; 25 mug/ml); and 7) bCSP (25 mug/ml) + antagonist (5 mug/ml). Platelet-activating factor had distinct negative and positive dose effects on PGF and PGE-2 secretion, respectively, by explants from cyclic cows, whereas PG secretion was not altered by PAF in the endometrium of pregnant cows. Platelet-activating factor did not alter the level of an intracellular inhibitor of prostaglandin synthesis, whereas, bCSP increased the level of this inhibitor. Platelet-activating factor decreased the incorporation of [(3)H]leucine into tissue and secreted proteins for explants from cyclic cows. Lyso-PAF did not alter endometrial prostaglandin secretion. The effects of PAF but not of bCSP were blocked by the PAF-receptor antagonist. Platelet-activating factor altered PG and protein secretion by the endometrium from cyclic cows, and it may be a potential regulatory factor during early pregnancy if secreted by the bovine conceptus.     

Functional role of local angiotensin-converting enzyme (ACE) in adrenal catecholamine secretion in vivo

The aim of the present study was to investigate whether exogenous angiotensin I (AngI) is locally converted to angiotensin II (AngII), which in turn results in an increase in the adrenal catecholamine (CA) secretion in the adrenal gland in anesthetized dogs. Plasma CA concentrations in adrenal venous and aortic blood were determined by an HPLC-electrochemical method. Adrenal venous blood flow was measured by gravimetry. Local administration of AngI (0.0062 to 6.2 microg, 0.0096 to 9.6 microM) to the left adrenal gland resulted in significant increases in CA output in a dose-dependent manner. Following administration of 0.62 microg (0.96 microM) of AngI, adrenal epinephrine and norepinephrine outputs increased from 20.8+/-13.6 to 250.9+/-96.4 ng x min(-1) x g(-1) (p<0.05, n = 5) and from 2.8+/-1.7 to 29.6+/-11.1 ng x min(-1) x g(-1) (p<0.05, n = 5), respectively. From the same left adrenal gland, the output of AngII increased from -0.02+/-0.04 to 26.39+/-11.38 ng x min(-1) x g(-1) (p<0.05, n = 5), while plasma concentrations of AngII in aortic blood remained unchanged. In dogs receiving captopril (12.5 microg, 0.5 mM) 10 min prior to AngI, the net amounts of CA and AngII secreted during the first 3 min after AngI were diminished by about 80% (p<0.05, n = 5) compared with those obtained from the control group. There was a close correlation (r2 = 0.91, n = 6) between the net increases in AngII and CA outputs induced by AngI. The results indicate that the local angiotensin converting enzyme is functionally involved in regional AngII formation in the canine adrenal gland in vivo. The study suggests that AngII thus generated may play a role in the local regulation of adrenal CA secretion.     

The relationship between adrenal vascular events and steroid secretion: the role of mast cells and endothelin.

The actions of ACTH on the adrenal cortex are known to be 2-fold. In addition to increased steroidogenesis, ACTH also causes marked vasodilation, reflected by an increased rate of blood flow through the gland. Our studies, using the in situ isolated perfused rat adrenal preparation, have shown that zona fasciculata function and corticosterone secretion are closely related to vascular events, with an increase in perfusion medium flow rate causing an increase in corticosterone secretion, in the absence of any known stimulant. These observations give rise to two important questions: how does ACTH stimulate blood flow; and how does increased blood (or perfusion medium) flow stimulate steroidogenesis? Addressing the first question, we have recently identified mast cells in the adrenal capsule, and shown that Compound 48/80, a mast cell degranulator, mimics the actions of ACTH on adrenal blood flow and corticosterone secretion. We have also demonstrated an inhibition of the adrenal vascular response to ACTH in the presence of disodium cromoglycate, which prevents mast cell degranulation. We conclude, therefore, that ACTH stimulates adrenal blood flow by its actions on mast cells in the adrenal capsule. Addressing the second question, we looked at the role of endothelin in the rat adrenal cortex. Endothelin 1, 2 and 3 caused significant stimulation of steroid secretion by collagenase dispersed cells from both the zona glomerulosa and the zona fasciculata. A sensitive response was seen, with significant stimulation at an endothelin concentration of 10(-13) mol/l or lower. Endothelin secretion by the in situ isolated perfused rat adrenal gland was measured using the Amersham assay kit. Administration of ACTH (300 fmol) caused an increase in the rate of immunoreactive endothelin secretion, from an average of 28.7 +/- 2.6 to 52.6 +/- 6 fmol/10 min (P less than 0.01, n = 5). An increase in immunoreactive endothelin secretion was also seen in response to histamine, an adrenal vasodilator, which stimulates corticosterone secretion in the intact gland, but has no effect on collagenase-dispersed cells. From these data we conclude that endothelin may mediate the effects of vasodilation on corticosterone secretion, and this mechanism may explain some of the differences in response characteristics between the intact gland and dispersed cells.     

Adrenocorticotropin secretion rates following histamine injection in adult and newborn dogs.

The metabolic clearance rate (MCR) for ACTH in adult dogs was previously shown not to vary significantly with varying plasma ACTH concentrations or among dogs. This is confirmed here for pups aged 1-7 days. Hence, ACTH secretion rates can be continuously calculated from a continuous function of plasma ACTH vs. time. Each of seven adult dogs under Nembutal anesthesia received two or three intravenous (i.v.) injections of histamine with increasing doses. The first injections in each dog ranged from 7 to 50 mug/kg, while the last dose was 62-108 mug/kg. A total of 16 injections were given. Twelve pups (two litters of six) aged 1-7 days each received one injection of histamine of 76-116 mug/kg (i.v.). ACTH concentrations in plasma were determined by an adrenal cell suspension bioassay before, and 6 times after each injection. Nine pups also underwent determinations of their MCR for ACTH, with plateau concentrations determined at three times during an ACTH infusion. Continuous curves of ACTH secretion rates were calculated for all 28 histamine injections, showing that all except the 1-day-old pups secrete considerable ACTH when stressed. Compared to adult dogs, the pups show lower secretion rate peaks and shorter periods of rapid secretion. Changes in plasma glucocorticoids also suggest that the adrenal cortex of newborn dogs can respond to ACTH by increased glucocorticoid secretion.     

Hormonal and clinical responses to prednisone treatment in adolescents with congenital adrenal hyperplasia

The effects of prednisone therapy and the withdrawal of prednisone for 3 days on hormonal relationships was investigated in 6 adolescent patients, age 10--19 years with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. Prednisone continuously suppressed adrenal release of 17 alpha-hydroxyprogesterone (17-OHP) in 4 patients and adequately controlled 17-oxosteroid (17-OS) excretion in 5. Serum dehydroepiandrosterone sulfate (DS) concentrations were not elevated during or 3 days after withdrawal of medication. Growth hormone (GH) secretion was not suppressed by prednisone. Withdrawal of treatment was associated with a decrease in the follicle-stimulating hormone (FSH) to luteinizing hormone (LH) ratio in 5 patients and a rise in serum testosterone in 4. The clinical courses of these patients emphasize the difficulty in achieving optimum control.     

Mechanism of dissociation of cortisol and adrenal androgen secretion after removal of adrenocortical adenoma in patients with Cushing's syndrome

We investigated the mechanism of dissociation of cortisol and dehydroepiandrosterone sulfate (DHEA-S) secretion by the adrenal glands after the removal of an adrenal gland containing an adrenocortical adenoma in a patient with Cushing's syndrome. After removal of the adrenocortical adenoma, the serum cortisol rapidly decreased from 24.6 +/- 6.4 micrograms/dl (mean +/- SD, n = 6) to 0.7 +/- 0.5 micrograms/dl. Serum DHEA-S levels were 15 +/- 14 micrograms/dl and 6 +/- 9 micrograms/dl before and after surgery, respectively, and significantly lower than the control values. Serum cortisol levels reverted to normal levels 1.5 to 3 years after the surgery. On the other hand, DHEA-S levels reverted to normal 5 to 7 years after the serum cortisol levels had normalized. Monolayer cultures of normal human adrenal cells obtained at adrenalectomy in patients with advanced breast cancer and atrophic adrenal cells adjacent to the adrenocortical adenoma in patients with Cushing's syndrome were used to study the mechanism of the dissociation of cortisol and DHEA-S secretion. ACTH caused significant increases in the productions of pregnenolone (P5), progesterone (P4), 17-hydroxypregnenolone (17-OH-P5), 17-hydroxyprogesterone (17-OH-P4), DHEA, DHEA-S, androstenedione (delta 4-A), and cortisol. The amounts of 17-OH-P5 and 17-OH-P4 produced by ACTH in atrophic adrenal cells were significantly greater than those in normal adrenal cells. The amounts of DHEA, DHEA-S and delta 4-A produced by ACTH in atrophic adrenal cells were significantly smaller than those of normal adrenal cells. The conversion rate of 17-OH-[3H]P5 to 17-OH-[3H]P4 and 11-deoxy-[3H] cortisol was higher in atrophic adrenal cells than in normal adrenal cells, but the conversion rate to [3H]DHEA, [3H]DHEA-S and [3H]delta 4-A was significantly lower in atrophic adrenal cells than in normal adrenal cells. These results suggest that the dissociation of cortisol from DHEA-S after the removal of adrenocortical adenoma is a probably due to diminished C17,20-lyase activity in the remaining atrophic adrenal gland.     

Steroid production by quartered and capsular rat adrenal gland in response to haemorrhage.

60 min after rapid bleeding (1.5--2.0 per cent of b. w.) both aldosterone and corticosterone production rate by quartered rat adrenals were found to be elevated. However, no difference was observed in the rate of aldosterone and corticosterone production by capsular adrenals of sham operated and hypovolaemic rats. Corticosterone production rate by decapsulated adrenals was much more higher after haemorrhage than in the control group. The same alterations could be observed incubating adrenal tissue with ACTH (0.3 mug per ml). Steroid production rate by quartered adrenals of sodium deficient rats was not affected by high in vitro concentration of angiotensin II (2.5 mug per ml). It is concluded that the effect of acute blood loss on corticosteroid biosynthesis of the rat is mediated by ACTH alone.     

Hormonal regulation of thermogenesis in goslings. Possible role of the thyroid gland.

The experiments performed on 90 male goslings showed that 6 h cold exposure (5 +/- 1 degree C) of the specimens 3, 10 and 21-day-old increases considerably 131I uptake by their thyroid gland. After single subcutaneous injection of thyroxine (100 mug/kg) no significant alterations of the metabolic rate, during 4 h measurements, in comparison with the pre-injection value were observed. Since, in control birds about 17% decrease of the metabolic rate within the same time occurred, as the effect of fasting, it was concluded that thyroxine does have the calorigenic effect. The metabolic rate of the goslings 5 to 7-day-old treated with thyroxine for four consecutive days (100 mug/kg daily) and the control ones was very similar. In the older goslings (22--24 days) thyroxine treatment significantly elevated the metabolic rate. Direct (extrathyroid) effect of TSH on heat production, did not occur in goslings.     

Pregnanetriolone, a normal steroid metabolite: its excretion by normal, Cushing's syndrome and congenital adrenal hyperplasia subjects.

Synthesis of 3H-pregnanetriolone permitted the estimation of pregnanetriolone in urine with a sensitivity in excess of most previous claims. A good correlation (r = +0.97) was obtained between the values from gas liquid chromatography and those of a double isotope derivative method. In contrast to previous reports, these methods indicated that pregnanetriolone is excreted by normal adults. Urinary pregnanetriolone levels were 18-59 mug/24hr for normal subjects, 35-290mug/24hr in Cushing's syndrome and 250-7000 mug/24hr with congenital adrenal hyperplasia. It is concluded that pregnanetriolone is a normal steroid metabolite and its occurrence in Cushing's syndrome does not necessary indicate an abnormal steroid biosynthetic pathway.     

Mutagenesis by simian virus 40. I. detection of mutations in Chinese hamster cell lines using different resistance markers.

The mutagenic action of SV40 in permanent lines of Chinese hamster cells (CHO-K1 and V79) was investigated with the aid of different resistance markers. The markers studied had resistance to 8-azaguanine (25 and 30 mug/ml), aminopterin (3.3--5.5X10(-3) mug/ml), colchicine (6.5 and 7.0X10(-2) mug/ml) and 5-bromodeoxyuridine (50--120 mug/ml), respectively. After virus infection the mutation frequencies were increased by one (azaguanine, aminopterin) and two (colchicine) orders of magnitude as compared with spontaneous mutation frequencies. In contrast, it was not possible to enhance the frequency of mutation to BUdR resistance. On the other hand, the ability to proliferate in HAT medium was induced in three of five BUdR-resistant cell clones by infection with SV40. The resistance induced by SV40 was stable when isolated clones were cultured under non-selective conditions. Mechanisms are proposed that may be responsible for the mutagenic action of SV40.     

Des-Asp-1-angiotensin II. possible role in mediating the renin--angiotensin response in the rat.

Angiotensin II and its heptapeptide fragment, Des-Asp-1-angiotensin II, produced a striking increase in aldosterone secretion in rats pretreated with dexamethasone and morphine to reduce ACTH release. 1-Sar-8-Ala-angiotensin II (10 mug/kg min-1) given simultaneously with angiotensin II (1 mug/min) blocked the aldosterone response to angiotensin II in rats pretreated to reduce ACTH release. In contrast, 1-Sar-8-Ala-angiotensin II at the same dose failed to block the steroid response to Des-Asp-1-angiotensin II (1 mug/min) but a larger dose of 50 mug/kg min-1 of the angiotensin II antagonist blocked completely both the aldosterone and the corticosterone responses to 1 mug/min of Des-Asp-1-angiotensin II. From these data it is suggested that the heptapeptide has a higher affinity for zona glomerulosa receptors than the octapeptide and that Des-Asp-1-angiotensin II mediates, at least in part, the steroidogenic response to the renin-angiotensin system in the rat. The pressor response to Des-Asp-1-angiotensin II was approximately 50% of that produced by the octapeptide in the rat, and 1-Sar-8-Ala-angiotensin II was as effective in partially blocking the pressor response to the octapeptide as in inhibiting the heptapeptide. The present observations indicate a dissociation of adrenal cortex and peripheral arteriolar receptors in their affinity for angiotensin.     

Identification of 5 beta-pregnane and 5 beta-androstane derivatives in adrenal venous and peripheral blood plasma of the female possum (Trichosurus vulpecula)

In the possum a marked sex difference has been found in the steroids in adrenal venous plasma. Four 5 beta-pregnane and four 5 alpha (beta) androstane derivatives together with ten 4-ene-3-keto steroids were isolated from the adrenal venous plasma of the female and definitively identified by gas chromatography-mass spectrometry. The major reduced steroids were: 5 beta-pregnane-3 alpha,17 alpha-diol-20-one and 5 beta-pregnane-3 alpha,17 alpha,20 alpha-triol, at concentrations of 52 +/- 12 micrograms/100 ml and 44 +/- 8 micrograms/100 ml mean +/- SEM respectively. The concentration of cortisol was 198 +/- 47 micrograms/100 ml. The concentration of the 2 reduced steroids in peripheral plasma were approx. 100 times less. In contrast the adrenal venous plasma of a male contained 14 steroids of which only three, found in trace amounts, were reduced. The results confirm previous in vitro observations that reduced steroids are produced by the adrenocortical special zone, which is only present in the female. The physiological significance of the presence of reduced steroids of adrenocortical origin in the circulation of the female possum is discussed.     

Comparative physiological characteristics of the action of pentagastrin on gastric secretion in fish, frogs, turtles and chickens]

The same preparation of pentagastrin, which is highly effective in dogs (threshold dose 0.3 mug/kg), has been tested on fishes, frogs, tortoises and hens. In fishes (rays), the threshold dose was equal to 50 mug/kg; the drug only increased juice secretion, but did not decrease pH of the juice. In frogs, the effective dose was equal to 25, in tortoises -- to 50 mug/kg, the drug increasing the secretion of both the juice and HCl. The effect of the drug exhibits seasonal variations, being absent in winter period. In hens, the threshold dose is equal to 5 mug/kg; the drug increases both the volume of the juice and HCl production. In frogs and hens, similar to that in dogs (tortoises were not studied in this respect), pentagastrin also increases the production of proteases of gastric juice. It is suggested that in the animals studied pentagastrin is a specific stimulator of gastric secretion.     

Determination of mevalonate in blood plasma in man and rat. Mevalonate "tolerance" tests in man.

A method is described for the determination of mevalonate in ultrafiltrates of blood plasma. The method depends on the phosphorylation of mevalonate with [gamma-32P]ATP and mevalonate kinase to 5-[32P]phosphomevalonate, and the subsequent isolation of the 5-[32P]phosphomevalonate together with known amounts of added 5-phospho[14C]mevalonate by ion-exchange chromatography. The 32P/14C ratio in the isolated 5-phosphomevalonate is a linear function of the mevalonate content of the samples. The smallest amount that can be determined is 1--2 pmol. The fasting level in human plasma varied between 20 and 75 pmol/ml. Human red blood cells absorb mevalonate from plasma relatively slowly; their maximum storage capacity is about 1.3 pmol/10(6) red cells. An oral and intravenous "mevalonate tolerance test" in man is described that can be carried out with 200 and 30 mumol. respectively, of the unlabeled (RS)-mevalonate in a 70-kg man. Beer and wine contain mevalonate at a concentration of 3--8 microns, too low to provide a significant amount of mevalonate even for heavy drinkers. The mevalonate content of the plasma from the blood of the vena cava inferior of male rats varied between 81 and 502 pmol/ml and is positively related to the levels of liver 3-hydroxy-3-methylgultaryl-CoA reductase, suggesting that the liver is probably the main source of mevalonate circulating in blood. The plasma of renal venous blood contained only 33--85% as much mevalonate as the arterial plasma.     

Localization of aldosterone-producing adenoma: venous sampling in primary aldosteronism

Adrenal venous sampling of blood was performed for nine patients with aldosterone-producing adenoma (APA). Measurement of adrenal venous aldosterone is useful for localization of APA but difficult, because catheterization of the right adrenal vein is not easy, and the blood is diluted by nonadrenal flow. To solve these problems, levels of aldosterone (A; ng/dl) and cortisol (C; micrograms/dl) were measured in samples from the left adrenal vein (LAV) and the inferior vena cava (IVC), and the LAV A/C and (LAV A/C)/(IVC A/C) ratios were calculated. These ratios were also obtained for 16 patients with essential hypertension. The adenoma could be localized in three of the nine cases by the measurement of aldosterone alone, but the use of a LAV A/C ratio greater than 5 x 10(-3) and a (LAV A/C)/(IVA A/C) ratio less than 1.0 as criteria separated the patients into those with a left APA, right APA, or essential hypertension. Consequently, adrenal venous sampling and the calculation of these ratios enables preoperative localization of APA with more accuracy, especially when the tumor is small or the result of CT and adrenal scintigraphy is not consistent.