Failure to demonstrate a natriuretic effect of neurophysin in rats

Partly purified rat neurophysin was tested for its possible natriuretic activity in acutely hypophysectomized saline-loaded rats (hypophysectomized 2 h prior to saline infusion). Such animals were unable to excrete the saline load. When partly purified rat neurophysin was injected i. p. in a dose of 40 microgram per animal (which corresponds to its content in one rat posterior pituitary) before saline loading, the sodium excretion was not different from that found in acutely hypophysectomized animals, but it was significantly lower than in normal saline-loaded rats. It was concluded that any apparent natriuretic effect of rat neurophysin could not be established by the present experiments under the experimental conditions used.