Changes in the prolactin-binding capacity of mouse hepatic membranes with development and aging

The objective of this study was to document the developmental changes in the prolactin-binding capacity of hepatic membranes of the female mouse. Prolactin-binding capacity was measured in the microsomal membranes of liver obtained from C3H female mice at various ages. Binding capacity of these membranes remained low until 21 days of age after which it increased and reached the adult levels by 44 days of age. Additional studies were made to observe this parameter in male and female mice during aging. Both female and male mice at 450-470 days of age had values of prolactin binding that were 66% and 79% that of the 77-day-old animals, respectively. A significant increase in membrane lipid microviscosity was observed in animals from both sexes at 450-470 days of age. This was in agreement with earlier studies that showed that prolactin receptors of hepatic membranes are modulated by changes in the membrane lipid microviscosity. These changes suggest that such modifications of cellular membranes are interrelated and that changes in the membrane microviscosity with aging may be a factor modulating cellular responses in older animals.