Potassium transfer from brain to blood during sustained hyponatraemia in the calf.

Publisher Website
Google Scholar
Abstract
The effects of hyponatremia on cerebral blood flow, oxidative metabolism and transfer of Na and K from the brain.sbd.CSF compartment to blood were examined in anesthetized calves 2-6 wk after birth. Dilutional hyponatremia was produced by administration of a long-acting antidiuretic hormone analog (desmopressin) and the infusion of hexose solutions of various concentrations. Cerebral blood flow was measured using a hydrogen clearance technique, and metabolism and cation transfer quantified by simultaneous determination of arterio-cerebral venous concentration differences. Sustained hyposmolar hyponatremia (plasma osmolality, 232 .+-. 1 m-osmol/kg; plasma Na, 117.1 .+-. 0.5 mmol/l) was associated with a fall in cerebral blood flow, and increase in measured net transfer of K from the brain CSF compartment to the circulation. CSF Na concentration and osmolality were both decreased. No alterations in these variables occurred during sustained isosmolar hyponatremia (plasma osmolality, 284 .+-. 2 m-osmol/kg; plasma Na, 119.9 .+-. 0.2 mmol/l). The route, mechanism and time course of K loss from brain during hyponatremia were discussed.