The effect of alcohol on quantitative and qualitative changes in luteinizing hormone (LH) in the female rat

In order to study the impact of short-term ethanol feeding on pituitary luteinizing hormone (LH) levels, LH release and hormone microheterogeneity, 28 female oophorectomized rats were fed either a diet containing 36% ethanol or an isocaloric diet without ethanol for 16 days. On the 14th day of the experiment, all rats were given 50 micrograms of estradiol subcutaneously to provide a uniform steroid milieu and to induce an LH surge, and sacrificed 48 hours later. Total levels of pituitary and serum immunoreactive LH were identical between the ethanol and control groups. However, when pituitary LH was analyzed by isoelectric focusing on agarose gel a distinct difference was found. Four distinct immunoreactive peaks at pI's 3.50-4.55, 5.20-6.50, 7.00-7.50, 8.15-9.30 were noted. Ethanol-treated animals exhibited an 8-fold increase in the acidic LH subspecies in the pI range 3.50-4.55 and similarly more LH was determined at pI 7.00-7.50 compared to controls (P less than 0.01). More LH was found at the basic pI's from control pituitaries, compared to LH from the ethanol-exposed animals (P less than 0.01). In summary, short-term ethanol feeding in the female rats does not cause quantitative changes in pituitary LH levels or in the estrogen-induced LH surge. However, qualitative changes are present in isoelectric focusing patterns. A significant shift to the more acidic species of the pituitary LH isohormone was noted for ethanol-fed animals as compared to controls. These qualitative changes in the LH molecule, seen before quantitative changes could be appreciated, may help to explain why excessive exposure to alcohol results in reproductive impairments both in rats and in humans.