| Name | Bruno |
| Surname | Varriale |
| Institution | Università degli Studi della Campania Luigi Vanvitelli |
| bruno.varriale@unicampania.it | |
| Address | Department of Experimental Medicine, Molecular Genetics Laboratory, University of Campania "Luigi Vanvitelli", Via Costantinopoli 16, 80138, Naples, Italy |
The effects of a GnRH analog (GnRHA), D-Ser-t-Bu6,desGly-NH2(10) (HOE 766) on spermatogenesis were analyzed in the frog, Rana esculenta. Intact animals caught at two different periods of the year (January and March) were treated with HOE 766 (GnRHA, 45 ng/g BW) at low (4 +/- 1 C) and high (22 +/- 2 C) temperatures. Hypophysectomized frogs were used also and, in addition to GnRHA, these animals were treated with crude pars distalis homogenate. In vitro incubations were carried out at 15 C, for 0, 6, and 24 h with the addition of 1 microgram GnRHA. Half of each testis was used as the untreated control. Histological sections of the testes were analyzed for the evaluation of the mitotic index of the primary spermatogonia. Intact March animals had mitotic indices higher than January animals. GnRHA treatment elicited an increase of the mitotic index in both intact and hypophysectomized animals. High temperature potentiated the GnRHA effect while low temperature favored pars distalis treatment. In conclusion, the present results are consistent with the fact that in the frog, R. esculenta, the magnitude of spermatogonial proliferation is temperature dependent, and for the first time it is shown that GnRH-like substances have direct stimulatory effect on the mitotic activity of the primary spermatogonia in a vertebrate.
The profiles of estradiol (E2), progesterone (P), and androstenedione (A), have been studied for the first time in cyclic Gentile di Puglia ewes. Estradiol peaks at estrus whereas progesterone levels are high during the luteal phase. Androstenedione does not show meaningful cyclic fluctuation. All hormones examined show also a pulsatile pattern when plasma was collected hourly.
Seasonal plasma testosterone and androstenedione levels were determined by radioimmunoassay in the Gentile di Puglia ram. Androstenedione remains steady throughout the years, while testosterone shows seasonal changes. Testosterone is at high levels in winter, spring and summer and drops to a low concentration in autumn.
Testicular testosterone was determined by radioimmunoassay in the frog (Rana esculenta) kept in total darkness, at a high or a low temperature (24 or 4 degrees C), and treated with a gonadotrophin-releasing hormone analog (GnRHa, HOE 766). Prolonged exposure to dark conditions seemed to inhibit hypotalamic functions. Moreover, it is shown that high temperature interacts positively with GnRHa treatment on testicular testosterone concentration.
The summary testicular effects of an agonistic analogue of gonadotropin-releasing hormone (buserelin, GnRHa) have been studied in vitro and in vivo in the frog, Rana esculenta. During 3 h incubation GnRHa (8 X 10(-7) M) potentiated pituitary factors in stimulating testosterone production by minced testes in vitro. After 6 h of incubation 8 X 10(-7) M GnRHa stimulated maximal testosterone output. Testes of 10-day hypophysectomized animals did not show any GnRHa effect in vitro. In vivo, a direct effect of GnRHa on testicular testosterone production was demonstrated in hypophysectomized animals, although this effect was temperature-dependent, requiring the frog to be maintained at a high temperature (24 degrees C). No effect of GnRHa was detectable in frogs kept at a low temperature (4 degrees C).