Histochemical correlates for differences in functional activity of kidneys from active and cold‐stored summer bats (Myotis lucifugus)

Fourteen female Myotis lucifugus from a summer colony were adapted to laboratory conditions for periods up to 60 days. Animals were then divided and exposed to the following conditions: (I) active bats exposed to normal summer laboratory temperature and humidity; (II) active bats exposed to normal summer laboratory temperature but low humidity; (III) cold‐stored bats; (IV) cold‐stored bats exposed to low humidity. All cold‐stored bats entered a state of apparent deep hibernation, carrying out characteristic reflexes upon being awakened. Their thyroid glands showed significant loss of secretory activity. Staining for ATPase activity (method of Wachstein and Meisel) on formalin‐fixed sections of kidney showed that there was increased infolding as well as increased enzymic activity of the plasma membranes of the proximal convolutions from all cold‐stored bats. Proximal convolutions from kidneys of active bats showed decreases in the degree of invagination of the plasma membranes with apparently expanding basal lamellae. Acid phosphatase activity (Gomori) was confined to “phagosomes” in the proximal convolutions of active bats; cold‐stored bats showed no activity. Staining with the periodic Schiff method showed irregular staining of the brush border of tubules from active bats; cold‐stored animals showed a regular brush border with this method. The results suggest that the histochemical methods employed reveal differences in kidney function between the active and cold stored animals.