Sex-dependent parameters related to electrolyte, water and glycoprotein secretion in rabbit lacrimal glands

Abstract

The lacrimal glands of males and females of various species differ with respect to several morphological, biochemical and functional characteristics. The purpose of this study was to determine the effect of sexual maturation on Na⁺,K⁺-ATPase, muscarinic cholinergic receptors and β-adrenergic receptors, which are closely related to the secretion of electrolytes and fluid by the gland, and on other membrane-associated enzymes, specifically galactosyltransferase and alkaline and acid phosphatase. Soluble and total membrane fractions were obtained from lacrimal glands of prepubertal (1.0 kg), pubertal (2 kg), and mature (4 kg) New Zealand white rabbits of both sexes. Prepubertal and pubertal rabbits exhibited no sex differences in the total amount of lacrimal gland protein or in any of the enzymes or receptors, with the exception of galactosyltransferase and alkaline phosphatase. Galactosyltransferase had higher total and specific activities in prepubertal and pubertal males, and alkaline phosphatase had higher specific activity in prepubertal males. As animals matured, total protein and activities of the enzymes increased, and several quantitative differences between males and females became apparent. Samples from mature females contained significantly less DNA and membrane and total protein. Specific activities of Na⁺, K⁺-ATPase, cholinergic receptors, galactosyltransferase, and acid and alkaline phosphatase were 40% to 80% greater (p < 0.05) in mature females. Total and specific activity for β-adrenergic receptors, on the other hand, were higher in the male rabbits. These findings suggest that sex hormones play a role in regulating the levels of expression of a number of enzymes and receptors, including several which are clearly involved in lacrimal secretory functions.