Vasant V. Patwardhan

Sex steroids and 5-en-3β-hydroxysteroids in specific regions of the human brain and cranial nerves

Sex steroids and 5-en-3 beta-hydroxysteroids were determined by radioimmunoassay in specific regions of the human brain, in the anterior and posterior pituitary, in one sensory organ, the retina and in the cranial nerves. Progesterone, androstenedione, testosterone and estrone were found in all areas of the brain and in all the cranial nerves but not in all cases. There was no sex difference except in the case of androstenedione where values were higher in women in some brain areas. Estrone values were always higher than those of estradiol in both men and women. No 5 alpha-dihydrotestosterone was detected in any of the samples studied. The values for pregnenolone, dehydroepiandrosterone and their sulfates were much higher than those of the sex steroids in all areas of the brain and in all the cranial nerves. Values for pregnenolone were greater than those of its sulfate while those of dehydroepiandrosterone were in general equal to or higher than those of its sulfate. The values for pregnenolone were greater than those of dehydroepiandrosterone. There were no obvious regional differences in the concentrations of the 5-en-3 beta-hydroxysteroids either in specific areas of the brain or in the cranial nerves. But there was a definite trend for the free dehydroepiandrosterone values to be higher in women. The possible significance of these observations is discussed.

Luteal phase variations in endogenous concentrations of prosta-glandins PGE and PGF and in the capacity for their in vitro formation in the human corpus luteum

One evidence for a luteolytic role for prostaglandin F2 alpha in the human is the increase in luteal PGF at times corresponding to luteolysis as reported earlier by us and other groups. There have been other contradictory reports on this point. In the present experiments we have measured the concentrations of PGE and PGF in 16 more human corpora lutea and have determined the capacity of those tissues to form PGE and PGF in vitro. PGF concentrations were highest in the mid luteal phase but were accompanied by high PGE concentrations. On the other hand, in the late luteal phase PGF concentrations, lower than in mid luteal but generally higher than in early luteal phase, were significantly higher than PGE concentrations. This pattern in PGE and PGF concentrations was also evident in the capacity of these tissues to form these compounds in vitro. In view of the known capacity of PGE2 to counteract the luteolytic effect of PGF2 alpha, these variations in the relative concentrations of PGE and PGF during the luteal phase may be of significance in the process of luteolysis in the human.

Concentration of prostaglandins PGE and PGF, estrone, estradiol, and progesterone in human corpora lutea

The concentrations of prostaglandins PGE and PGF, estrone, estradiol and progesterone in human corpora lutea were measured by radioimmunoassay at various stages of the luteal phase of the menstrual cycle. The concentrations of PGF were found to be significantly higher in both the mid and late luteal phases than in the early luteal phase. In the mid luteal phase there was a concomittant increase in PGE levels, but these levels had declined in the late luteal phase. Steroid concentrations were generally lower in the late luteal phase. It has been postulated that in the human corpus luteum locally produced prostaglandins may be responsible for luteolysis. Our data on the concentrations of PGF and PGE in corpora lutea at various stages of the luteal phase support such a possibility.

Effect of prostaglandin F2α on the hCG-stimulated progesterone production by human corpora lutea

Abstract The effect of prostaglandin PGF2α on the hCG stimulated and basal progesterone production by human corpora lutea was examined in vitro . hCG (40 i.u./ml) stimulated progesterone formation in corpora lutea of early (days 16–19 of a normal 28 day cycle), mid (days 20–22) and late (days 23–27) luteal phases. This stimulation was inhibited by PGF2α (10 μg/ml) in corpora lutea of mid and late luteal phases. PGF2α alone did not show a consistent effect on basal progesterone production. The inhibition of hCG stimulated progesterone production by PGF2α at times corresponding to luteolysis indicates a role for that prostaglandin in the process of luteolysis in the human corpus luteum.

Effect of heterosexual olfactory and visual stimulation on 5-en-3β-hydroxysteroids and progesterone in the male rat brain

Pregnenolone, dehydroepiandrosterone and progesterone were measured in specific areas of the brain and in the retina of young adult male rats exposed to the scent or to the scent and view of young cycling females and compared to the levels obtained in males similarly exposed to other males (control). All the steroid values observed were much higher than those found in plasma, varied considerably from one area to another and responded sometimes in opposite directions to stimulation of young adult males by the scent or by the scent and view of cycling females. In male rats exposed to the scent of young cycling females pregnenolone decreased significantly only in the olfactory bulb in comparison with the controls. There were no significant changes in dehydroepiandrosterone or progesterone in this case. When male rats were exposed to the scent and view of female rats, pregnenolone again decreased significantly in the olfactory bulb while dehydroepiandrosterone increased significantly in the olfactory bulb and the retina and progesterone decreased significantly in the hypothalamus, amygdala and parietal cortex. These results are discussed in relation with a possible new role for certain steroids in neuroregulatory mechanisms related to behaviour.

In vitro steroid metabolism by rat retina

We have previously detected progesterone, dehydroepiandrosterone, androstenedione, testosterone and estrone in rat retina. The present experiments show that the presence of these steroids in the retina may not be due to local biosynthesis. On the other hand, they demonstrate considerable 5 alpha-reductase and 3 beta-hydroxysteroid dehydrogenase activities in the rat retina. The significance of these activities in the retina is discussed.

In vitro [7-3H]-testosterone metabolism by the rat ventral prostate—Effect of some exogenous compounds

Abstract Fragments of rat ventral prostate were incubated in vitro with [7-3H]-testosterone and the effect of some compounds on testosterone metabolism in this system was studied. Progesterone, 17-hydroxyprogesterone and ethynylestradiol inhibited the formation of dihydrotesterone (DHT), 3α-androstanediol, 5α-androstanedione and androsterone. There was a concomitant apparent stimulation of 17β-hydroxysteroid dehydrogenase activity. Medroxyprogesterone acetate (MPA) had no effect on formation of DHT but inhibited formation of 3α-androstanediol. This inhibition of 3a-hydroxysteroid dehydrogenase activity was confirmed when [4-14C]-DHT was incubated with the prostatic tissue in the presence of MPA. Prostaglandin E2 or the presumed absence of prostaglandins had no effect on 5α-reduction of testosterone in this system.

Effect of prostaglandins on the in vitro steroidogenesis in human ovarian tissues

This is a brief report of preliminary findings from in vitro studies of the effect of PGs (prostaglandins) on progesterone formation in human corpora lutea and on the utilization of C21 steroids by the luteal and follicular compartments of the ovary. Ovaries were obtained from cyclic women undergoing ovariectomies for therapeutic purposes. The laboratory procedures employed in the study are explained. Results are tabulated. PGE2 stimulated progesterone biosynthesis in the corpus luteum as measured by tissue content and by de novo synthesis from acetate-1-14C. PGE2 also stimulated the biosynthesis of DPS (digitonin-precipitable sterols) from acetate. These results confirm findings of other researchers. In 1 of the experiments, PGF2alpha failed to demonstrate stimulation of progesterone biosynthesis in the human corpus luteum as measured by tissue progesterone content after incubation. Both PGF2alpha and PGE2 showed generally stimulatory effects on the utilization of exogenous labelled progesterone for the formation of androgens and estradiol by the human corpus luteum. In the follicular tissue, however, PGE2 showed an inhibitory effect on the formation of androgens and progesterone from exogenous labelled pregnenolone. No significant amounts of estrogens were biosynthesized in these experiments. These preliminary results must be confirmed by measurement of the endogenous steroidal concentrations in the tissues.

Effect of 17-hydroxyprogesterone (17OHP) on the in vitro metabolism of labelled C21 steroids by bovine adrenals

Abstract In the biosynthesis of many of the steroidal hormones that are formed from C 21 steroid precursors, 17-hydroxy-progesterone (17OHP) serves as an important intermediate. In the present experiments, the effect of 17OHP on the metabolism of labelled C 21 steroids by bovine adrenals was studied by in vitro incubations. It was observed that microgram amounts (50 μgs/ml of incubation medium) of 17OHP 1) reduced the utilization of labelled pregnenolone (80–90% in control, 28–51% in presence of 17OHP) and progesterone (71–79% in control, 31–34% in presence of 17OHP), 2) inhibited the formation of progesterone (60% or more inhibition), corticosterone (42% or more inhibition) and aldosterone from labelled pregnenolone and 3) inhibited the formation of corticosterone from progesterone (80% inhibition). Smaller amounts of 17OHP (up to 10 μgs/ml) also showed these effects, although to a lesser degree. Presence of exogenous 17OHP, however, showed no effect on the pathways for the formation of cortisol and androstenedione from labelled C 21 steroids. Both these compounds were observed to be formed mainly through 17OHP both in the presence and absence of exogenous 17OHP.

Pregnenolone binding sites in the rat olfactory bulb

High concentrations of pregnenolone and its sulfate have been found in several areas of rat and human brain and seem to be controlled by local mechanisms. In the present experiments we have demonstrated pregnenolone binding sites in the cytosolic fraction of the rat olfactory bulb. The pregnenolone binding component showed a Kd = 2.34 +/- 0.66 x 10(-7) M and Nmax = 7.25 +/- 1.20 pmol/mg protein. Pregnenolone, pregnenolone sulfate and 17OH-pregnenolone competed equally for the binding sites while other steroids were less competitive. Protease and trypsin inhibited binding by 48 and 60% respectively. Sucrose density gradient analysis showed a minor peak at 4.6 s and a major one at 3.6 s. After gel filtration chromatography the pregnenolone binding component appeared as 2 peaks corresponding to molecular weights of approximately 150 and 220 kDa. Heating at 60 degrees C increased binding by 150%. These results indicate that the olfactory bulb pregnenolone binding component is complex in nature. Rat plasma also bound pregnenolone. Plasma binding sites could be partially differentiated from those in the olfactory bulb on the basis of susceptibility to lipoprotein lipase, effect of heating and mobility during polyacrylamide gel electrophoresis.