Cytochemically assayable Na+,K+-ATPase inhibition by Milan hypertensive rat plasma.

Abstract

SUMMARY The ability of plasma from 3-and 9-week-old Milan hypertensive rats and their nor motensive controls to inhibit Na + ,K+-adenosine triphosphatase (ATPase) was studied using cytochemical bioassay techniques in fresh tissue. With a validated cytochemical bioassay that measures the capacity of biological samples to stimulate glucose-6-phosphate dehydrogenase activity in guinea pig proximal tubules as an indication of their capacity to inhibit Na+,K+-ATPase, the mean gIucose-6-phosphate dehydrogenase-stimulating ability of the plasma of the 9-week-old Milan hypertensive rats and their normotensive controls was 586.0 ± 88 and 23.4 ± 8.3 U/ml (n = 7; p<0.001), while that of the 3-week-old Milan hypertensive rats (before the main rise in arterial pressure) and their normotensive controls was 99.9 ± 27.4and 7.8 ± 1.8 U/ml (n = 7; p<0.001). With the use of a semiquantitative cytochemical assay that measures Na+,K+-ATPase activity directly, plasma from the adult hypertensive rats had a much greater capacity to inhibit Na + ,K+-ATPase than the plasma of the control rats. The significantly raised levels found in the young hypertensive rats before the main rise in arterial pressure are consistent with the hypothesis that the rise hi the ability of plasma to inhibit Na+,K+-ATPase is due to an inherited renal difficulty in excreting sodium. (Hypertension 9:498-503, 1987) KEY WORDS • plasma • glucose-6-phosphate dehydrogenase-stimulating activity hypertensive rats • cytochemical assay • Na + ,K+-ATPase-inhibiting activity Milan

Cytochemical bioassays: every dog has its day

“…Absolute plasma vasopressin values obtained by the cytochemical bioassay were comparable to those measured by radioimmunoassay (r ¼ þ0.97, p < 0.001). This assay was later used to study hypertensive rats 41,42 and to determine the vasopressin levels in neonates. 43 One of the major drawbacks to these bioassays was the low throughput of the assay system.…”