Antiserum inhibition of the oestrous cycle in normal rats

EVIDENCE for the neutralization of pituitary gonadotrophic hormone activity in mammals by immunological procedures has been reviewed in several articles. The specificity of the hormone neutralizing (antihormone) effect of the antiserum has been suggested by many of the investigations reviewed, but there has been some question as to the specificity of this effect, because of the possible role of impurities or trace antigenic contaminants in the hormone preparations used1–4. A recent report5 describes the successful inactivation of a purified pituitary follicle-stimulating hormone (FSH); the marked follicular stimulation obtained by the injection of sheep FSH into immature hypophysectomized female rats could be completely inhibited with rabbit antiserum to the homologous FSH. This inhibitory effect was found to be dependent on the dosage of antiserum used. Other recent studies have reported the neutralization of endogenously secreted pituitary interstitial-cell stimulating hormone (ICSH) in the normal immature6–8 and mature8 male rat and in the immature female rat9, with the use of antiserum prepared against purified sheep ICSH.