High Dosage of Testosterone Propionate Increases Litter Production of the Genetically Obese Male Zucker Rat

Abstract

Summary

A high dose of testosterone propionate increases dramatically the litter production of young genetically obese male Zucker rats. Twenty milligrams testosterone injected subcutaneously once every three days over a 90-day period resulted in a nearly fourfold increase in the number of litters sired compared to sham-injected controls. The efficacy of the treatment attenuates with time. TP was ineffective in inducing litter production in older, more obese, males. Young obese males injected with TP exhibited a significantly reduced rate of weight gain compared to sham-injected controls. The findings are consistent with the hypothesis that the reproductive inadequacy of the genetically obese male rat may be due to a deficiency of circulating testosterone. The treatment of obese males with TP greatly increases the efficiency with which the obese (fafa) genotype may be produced and also avoids time-consuming testcrossing for identification of heterozygous (Fafa) individuals.