Reproductive hormone patterns in the female guinea-pig serum during the estrous cycle

Abstract

A study on hormone levels in daily consecutive serum samples during the guinea-pig estrous cycle was performed. Radioimmunoassay (RIA) of immunoreactive LH, FSH and prolactin (IR—LH IR-FSH and lR-prolaetin) developed for determination of rat pituitary hormone was used as well as RIA systems for estradiol-17β and progesterone. In oophorectomized animals estradiol, progesterone and IR-prolactin were undetectable while mean IR- LH and IR-FSH levels were 1.23 ug/l and 1.47 ug/l respectively as expressed in terms of rat hormone references. Prolactin could not be detected in serum during the reproductive cycle. During estrous cycles progesterone showed a biphasic pattern with undetectable levels (< 0.6 nmol/l) around ovulation. Increased levels were observed at the time of implantation. Estradiol-17β concentrations at non-surge time ranged between 0 and 116 pmol/l and a preovulatory peak (mean peak value 142.2 pmol) was noted. Serum IR-LH levels were between 0.2 and 0.8 pg/l and a prcovulatory peak was noted. Furthermore, a preovulatory lR—FSH peak was found (mean peak value 72.7 pg/l). The results indicate a close resemblance to the human reproductive cycle and the guinea-pig is suggested to be the laboratory animal ofchoice for studies on reproduction.