Ion Transport in Tonic and Phasic Vascular Smooth Muscle and Changes during Deoxycorticosterone Hypertension

Abstract

The washout of radioisotopes was studied in aorta, femoral artery and portal mesenteric vein from controls and rats made hypertensive with injection of deoxycorticosterone (DOC) acetate. Experiments were also conducted on tonic (pulmonary artery) and phasic (portal mesenteric vein) smooth muscle from rabbits. The rate constants for the washout of ⁴²K, ³⁶Cl and ²⁴Na from aorta were significantly elevated in the DOC hypertensives. Acute removal of extracellular K slowed the washout of ²⁴Na by 50%, however, the rate constant for the DOC group remained higher than the controls. Increased turnover of ⁴²K was also observed in the femoral artery and in a vessel (portal mesenteric vein) not exposed to the effects of high blood pressure in the rat. The rate constants for the washout of ⁴²K, ³⁶Cl and ²⁴Na from phasic smooth muscle in rabbit were greater than the tonic type. Ouabain significantly slowed ²⁴Na washout, however, the rate constant for the portal mesenteric vein remained higher than the pulmonary artery. DOC hypertension was associated with increased ion transport at several vascular sites. A similar change was observed for the phasic vascular smooth muscle from normal rabbits. A question is raised whether increased spontaneous activity of arteries reported to accompany DOC hypertension is the consequence of a membrane in transition from tonic to phasic behavior.

The kinetics of ouabain‐sensitive ionic transport in the rabbit carotid artery.

“…The finding that [Na]i is about 3 0 of total tissue Na agrees with results from other vessels (Jones & Miller, 1978;Wahlstr6m, 1973 Na exchange diffusion. Under Na-loaded conditions, 35 % of the carotid artery Na efflux was unaffected by ouabain, compared with 50 % reported for high-Na guinea-pig taenia coli by Casteels, Droogmans & Hendrickx (1973 a).…”

Oscillatory contractions in tail arteries from genetically hypertensive rats.

“…All preparations were allowed to equilibrate for 90 minutes before an experiment was begun The PSS was maintained at 37°C and was aerated with a mixture of 95% O 2 and 5% CO 2 Contractile responses to norepinephrine were measured in all experiments. Norepinephrine (1.8 X 10" 9 to 1.8 x 10" 5 M) was added to the organ bath, and the strips were allowed to contract for 20 minutes.…”

“…1 These alterations include increases in sensitivity to contractile agonists and altered membrane ionic permeabilities. Jones and Miller 2 have proposed that these changes in vascular smooth muscle function in hypertension may parallel the difference between tonic and phasic types of smooth muscle. Indeed, isolated blood vessels from hypertensive animals often exhibit spontaneous rhythmic contractions.…”

Amyloid β Protein Precursor Is Possibly a Heparan Sulfate Proteoglycan Core Protein

“…Because of similar findings in aortas and skeletal muscle of hypertensive rats treated with DOC-salt (Figs. 1A and 2), the up regulation of al-and 13-subunit mRNA expression is clearly not pressure-related, but could be secondary to alterations in Na+ flux induced by DOC-salt treatment; other studies have documented increased Na+ influx in these tissues (17,18). The increase in a1 mRNA correlates with increased vascular Na+,K+-ATPase activity in hypertensive rats treated with DOC-salt (19,20).…”