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Valle & Valle in 1943 demonstrated androgenic activity in the testes of Bothrops jararaca and Crotalus terrificus terrificus by bioassay. More recently Arvy (1962) has detected histochemically the presence of 3β-hydroxysteroid dehydrogenase in testicular interstitium of three species of reptiles. These data and reports of interstitial cell cycles correlated with reproductive periodicity in reptiles (Wilhoft & Quay, 1961; Wilhoft, 1963; Hahn, 1964; Wilhoft & Reiter, 1965) suggest the involvement of reptilian interstitial tissue in steroid synthesis.
It was therefore decided to determine the steroid biosynthesis of reptilian testes in vitro. Six mature Natrix sipedon pictiventris weighing 188–330 g. were obtained from their natural habitat in Florida during September. Testicular weight ranged from 1·71 to 4·08 g.; 16·5 g. of minced testicular tissue was distributed between 18–50 ml. flasks so that 800 mg. tissue were contained in each. Incubation conditions were those previously described (Callard & Leathem, 1964). Each flask was
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Department of Biology, Boston University, Boston, Massachusetts 02215, U.S.A.
(Received 9 January 1978)
Selective ablation of portions of the pituitary gland (Dodd, Evennett & Goddard, 1960) and indirect evidence from heterologous immunohistochemical (Mellinger & Dubois, 1973) or radioimmunoassay (Scanes, Follett & Goos, 1972) data has indicated that the anatomically discrete ventral lobe of the elasmobranch pituitary gland may be the sole source of gonadotrophins in these fishes. Bioassay studies have, however, given conflicting results. With a bioassay involving the uptake of 32P by the testes of 1-day-old chicks, Scanes, Dobson, Follett & Dodd (1972) found gonadotrophic activity only in the ventral lobe, whereas Firth & Vollrath (1973) showed gonadotrophic activity in both the ventral and median lobes of the pituitary gland of Scyliorhinus canicula when using the Xenopus oocyte meiosis assay. Thus there is still no agreement as to the nature and source of the gonadotrophin(s) in elasmobranchs.
The dispersed
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SUMMARY
The contractility of the oviduct of Chrysemys picta (the fresh-water turtle) was studied in vitro. Significant regional differences in contractile activity were observed. Contractions increased in amplitude and duration and decreased in frequency from the proximal to the distal end of the oviduct. Injections of oestradiol-17β in vivo increased the amplitude of contractions and decreased the duration of the rest period in segments taken from the distal end of the oviduct. In contrast, progesterone injections significantly reduced the duration of both contractile and resting periods.
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Prolactin is present in the reptilian pituitary (Grignon & Herlant, 1959; Nicoll & Bern, 1965; Nicoll, Bern & Brown, 1966) and its cellular site of origin has been ascribed to the caudal acidophils (Licht & Nicoll, 1969). This investigation is part of a study of the role of prolactin in the reproductive processes of female lizards.
Dipsosaurus dorsalis obtained during June-September were housed in wire mesh cages (60 × 30 × 30 cm., 10/cage) for 14 days with an available temperature gradient of 21–46° and a photoperiod of 16 hr. light-8 hr. dark. Food consisted of lettuce and water ad libitum. Growth hormone (GH), 200 μg. NIH-GH-S9 (0·2 i.u.)/100 g. body wt/day, and ovine prolactin, 1·0 mg. NIH-P-S8 (25 i.u.)/100 g. body wt/day, were administered s.c. in alkaline saline, and pregnant mare serum gonadotrophin (PMS, Ayerst 'Equinex '), 25 i.u./day i.p. in saline. Hypophysectomy by a buccal approach was verified by
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SUMMARY
The synthesis of steroids from [7α-3H]cholesterol, [7α-3H]pregnenolone and [7α-3H]progesterone by lizard and turtle ovarian tissues in vitro was studied. Progesterone, 17α-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone, oestrone and oestradiol were identified as products. In the turtle (Pseudemys), conversion of pregnenolone to progesterone was efficient, but transformation of progesterone to other steroids was relatively slow as indicated by the accumulation of progesterone over the incubation period. In Dipsosaurus, accumulation of radioactivity was greatest in testosterone, the quantities of which continued to increase at each sampling period. The rate of utilization of pregnenolone as a substrate was similar for the two species studied and the quantities of oestrone and oestradiol formed were lower in Pseudemys. The use of progesterone as precursor by Dipsosaurus ovarian tissue revealed a similar pattern of Δ4-steroid metabolism to that obtained with pregnenolone as precursor.
The effects of addition of purified follicle-stimulating hormone (FSH) and luteinizing hormone (LH) on the metabolism of [14C]cholesterol in vitro was studied using Pseudemys follicular tissue. The pattern of cholesterol metabolism was similar to that for pregnenolone in this species. The synthesis of pregnenolone, progesterone, dehydroepiandrosterone and androstenedione in vitro was significantly enhanced in the presence of LH. Follicle-stimulating hormone had no effect on steroid synthesis except for a decrease of androstenedione formation. The stimulatory effect of LH on steroidogenesis in vitro is discussed in relation to the literature suggesting that mammalian FSH, but not LH, stimulates all phases of reptilian ovarian function when injected in vivo.
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* Department of Physiology, Michigan State University, East Lansing, Michigan 48824, U.S.A., Departments of †Pure and Applied Zoology and ‡Animal Physiology and Nutrition, The University of Leeds, Leeds, LS2 9JT and §Department of Biology, Boston University, Boston, Massachusetts 02215, U.S.A.
(Received 24 June 1977)
Recent studies have shown that reptilian hypothalamic extract contains a prolactin releasing factor capable of acting on repitilian pituitary glands when incubated in vitro (Nicoll, Fiorindo, McKenee & Parsons, 1970; Hall, Chadwick & Callard, 1975b). It has also been suggested that steroids may influence the secretion of prolactin in reptiles (Callard, Doolittle, Banks & Chan, 1972). Müller, Sawano & Schally (1967) found evidence for a reptilian growth hormone (GH) releasing factor using a heterologous system. We have examined the control of the secretion of prolactin, GH and luteinizing hormone (LH) from the pituitary gland of the painted terrapin in vitro.
Pituitary glands and hypothalami were removed from
