The effects of neurohypophysial hormones on water and sodium balance in larval and adult bullfrogs ( Rana catesbeiana)

Abstract

1. 1. The injection of arginine vasoticin into bullfrogs at various stages of metamorphosis influences their body weight. In young tadpoles (stages IV–X) handling stress causes a pronounced loss of weight. This can be reduced or abolished by injecting AVT. Older tadpoles and adult elicit a typical Brunn effect; the intensity increases with stage of metamorphosis and reaches a maximum in adults. 2. 2. Doses of oxytocin up to 110 mμmoles/kg fail to elicit a water-balance response in tadpoles younger than stages XXII. Stage XXII animals show a small responses (106 per cent of initial weight in 2 hr) when injected with 22 mμmoles/kg; lower doses were not tested. Animals in stages XXIII to XXV respond to doses of 2·2 mμmoles/kg (103 per cent in 2 hr) and 22 mμmoles/kg (115 per cent in 2 hr). 3. 3. Arginine vasotocin (3·3 mμmoles/kg) causes a net uptake of sodium in tadpoles and adults. In tadpoles this is mostly attributable to a reduction in the efflux which probably reflects a decrease in the renal loss of the ion. In adults the uptake results from a faster influx indicating an effect on the skin.