ALPHA AND LUTEINIZING HORMONE BETA SUBUNIT MESSENGER RIBONUCLEIC ACIDS DURING THE RAT ESTROUS CYCLE

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Abstract
Alpha and LH beta subunit mRNAs were measured in pituitaries of 4-day cycling rats during the estrous cycle. A two-fold increase in a .alpha. mRNA occurred between 0800-2000 h on diestrus, but .alpha. mRNA concentrations were stable during other days of the cycle. LH.beta. mRNA concentrations were low during estrus and metestrus (11-16 pg cDNA bound/100 .mu.g pituitary DNA), but were elevated (27-30 pg) between 0800-2000 h on diestrus. A second increase in LH.beta. mRNA was observed on the afternoon of proestrus, prior to the onset of the surge with maxium values (45 pg) coincident with peak LH secretion. LH.beta. mRNA concentrations declined rapidly and had fallen to basal values by midnight on proetrus. These data show that alpha and LH.beta. mRNAs change in a similar manner during metestrus, diestrus and estrus, suggesting coordinate regulation of .alpha. and LH.beta. gene expression at these times. During the LH surge, however, LH.beta.v mRNA alone is increased, suggesting that the LH.beta. gene can be differentially expressed at times when maximum LH secretion is occurring.