title: Effects of hypoxia on vasopressin concentrations in cerebrospinal fluid and plasma of sheep.
abstract: The relationship between concentrations of vasopressin in plasma and cerebrospinal fluid (CSF) was examined under basal and hypoxic conditions in unanesthetized and unrestrained adult female sheep. Under basal conditions mean (+/- SE) concentration of vasopressin (4.1 +/- 0.3 pg/ml) in CSF was significantly (p less than 0.001) higher than the concentration in arterial plasma (2.4 +/- 0.2 pg/ml). There was a significant positive correlation between CSF and plasma vasopressin concentrations (r = 0.66, p less than 0.01). The introduction of severe hypoxia by exposure of the sheep to an inspired gas mixture of 5% O2 in N2, a known stimulus to systemic release of vasopressin, was associated with an increase in the concentration of vasopressin in plasma to 339 +/- 65 pg/ml and CSF to 19 +/- 3.9 pg/ml. This increase of vasopressin in CSF was delayed in time with respect to the increases in the plasma and of a lesser magnitude. With moderate hypoxia (10% O2 in N2 exposure) no increase in CSF or plasma vasopressin concentration was observed, suggesting a threshold response. Intravenous infusion of vasopressin to achieve plasma values comparable to those seen with hypoxia was not accompanied by a significant increase in CSF vasopressin concentration. Thus, severe hypoxia is a potent stimulus for release of vasopressin into both CSF and plasma. Furthermore, data suggest that vasopressin may be released into CSF via a separate route from that released into plasma.
mesh_terms: D000818:Animals; D005260:Female; D000860:Hypoxia / Q000097:blood / Q000134:cerebrospinal fluid*; D011863:Radioimmunoassay; D012756:Sheep; D013997:Time Factors; D014667:Vasopressins / Q000097:blood / Q000134:cerebrospinal fluid*
chemical_list: D014667:Vasopressins