The Frequency of Gonadotropin-Releasing Hormone Secretion Regulates Expression of α and Luteinizing Hormone β-Subunit Messenger Ribonucleic Acids in Male Rats

Publisher Website
Google Scholar
Abstract
The influence of GnRH pulse frequency on LH subunit mRNA concentrations was examined in castrate, testosterone-replaced male rats. GnRH pulses (25 ng/pulse) or saline to controls, were given via a carotid cannula at intervals of 7.5-240 min for 48 h. .alpha. and LH.beta. mRNA concentrations were 109 .+-. 23 and 30 .+-. 5 pg cDNA bound/100 .mu.g pituitary DNA, respectively, in saline controls. GnRH pulse intervals of 15, 30, and 60 min resulted in elevated .alpha. and LH.beta. mRNAs (P < 0.01) and maximum responses (4-fold, .alpha.; 3-fold, LH.beta.) were seen after the 30-min pulses. Acute LH release to the last GnRH pulse was seen after the 15-, 30-, and 60-min pulse intervals. In contrast, LH subunit mRNAs were not increased and acute LH release was markedly impaired after the rapid (7.5 min) or slower (120 and 240 min) pulse intervals. Equalization of total GnRH dose/48 h using the 7.5- and 240-min intervals did not increase LH subunit mRNAs to levels produced by the optimal 30-min interval. These data indicate that the frequency of the pulsatile GnRH stimuls regulates expression of .alpha. and LH.beta. mRNAs in male rats. Further, GnRH pulse frequencies that increase subunit mRNA concentrations are associated with continuing LH responsiveness to GnRH.