Complementary Deoxyribonucleic Acid (cDNA) Cloning and DNA Sequence Analysis of Rat Ovarian Inhibins*

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Abstract
Two forms of inhibitin (A and B), gonadal polypeptide hormones that selectively suppress the secretion of FSH from the anterior pituitary, have been characterized from the porcine and human species, each being composed of a common .alpha.-chain and one of two distinct, but homologous .beta.-chains, i.e. .alpha..beta.A and .alpha..beta.B. Using cDNAs encoding the porcine inhibin subunits we have cloned and sequenced the cDNAs encoding the .alpha., .beta.A, and and .beta.B chains of rat ovarian inhibin. Northern analyses of rat testicular RNA with rat ovarian cDNA probes show the presence of mRNAs encoding .alpha. and .beta.B chains, but no detectable mRNA encoding the .beta.a chain under our experimental conditions. This suggests that there may be specific and distinct physiological roles for inhibins A and B. In addition, if there is no extratesticular source of .beta.A mRNA, then the male rat may be devoid of the stimulators of the secretion of FSH, i.e. activin (.beta.A.beta.B) and homoactivin A (.beta.A.beta.A), which are derived from the .beta. subunits of the two inhibins.