Responsiveness of Adenylate Cyclase to Pituitary Gonadotropins and Evidence of a Hormone-Induced Desensitization in the Lizard Ovary

Seasonal-dependent effect of temperature on the response of adenylate cyclase to FSH stimulation in the oviparous lizard, Podarcis sicula

“…We have previously shown that FSH stimulates adenylate cyclase activity in follicular cell membranes and increases cAMP production in isolated ovaries in the lizard (Borrelli et al 1997). For this reason, we decided to use FSH- stimulated adenylate cyclase as a suitable biochemical marker of the ovarian activity in Podarcis sicula.…”

“…In reptiles, studies on the effect of gonadotrophins are usually performed with heterologous hormone preparations, because no reptilian gonadotrophin is available at the present time. However, in a previous study on the ovary of P. sicula, we demonstrated the presence in the lizard genome of nucleotide sequences homologous to mammalian follicle-stimulating hormone (FSH) (Borrelli et al 1997). As in other reptiles, heterologous FSH is capable of inducing oogonial proliferation, oocyte growth and differentiation, vitellogenesis (Limatola & Filosa 1989), estrogen production (Callard et al 1976, Lance & Callard 1978 and ovulation (L Borrelli, R De Stasio, CM Motta, E Parisi & S Filosa, unpublished observation).…”

“…As in other reptiles, heterologous FSH is capable of inducing oogonial proliferation, oocyte growth and differentiation, vitellogenesis (Limatola & Filosa 1989), estrogen production (Callard et al 1976, Lance & Callard 1978 and ovulation (L Borrelli, R De Stasio, CM Motta, E Parisi & S Filosa, unpublished observation). We have previously demonstrated that the hormone acts by stimulating adenylate cyclase activity present in the membranes of follicular cells (Borrelli et al 1997).…”

Effect of follitropin on adenylate cyclase activity and on FSH receptor mRNA expression during the ovarian cycle ofPodarcis sicula

“…Our previous studies suggested that follitropin might play an essential role in the reproduction of squamate reptiles. In the lizard Podarcis sicula, the administration of mammalian FSH induced oogonial proliferation, oocyte growth and differentiation, and vitellogenesis (Limatola & Filosa, 1989) by stimulating adenylate cyclase activity present in the membranes of follicular cells (Borrelli et al, 1997). Recently, we described the full nucleotide sequence of a cloned cDNA sharing a high level of similarity with FSH receptor of other vertebrates (Borrelli et al, 2001).…”

“…A control group was treated with a saline solution. The hormonal dosage and the time of treatment were chosen according to Borrelli et al (1997).…”