Salt-Induced hypertension in rats alters the response of isolated aortic rings to cromakalim

The effect of cromakalim, an opener of ATP-sensitive potassium (K atp) channel, on precontracted aortic rings from control and salt-loaded rats was studied in spague-Dawley rats. Salt-loading experiments involved the induction of hypertension by 6-week feeding of 80 g sodium chloride(NaCl)per kilogram(kg) diet while the control diet had 3 g NaCl per kg diet. Blood pressure and heart rate were determined by cannulation of a femoral artery under urethane/a-chloralose anaesthesia. Isolated aortic rings were mounted in tissue baths for isometric tension measurement. The sodium-potassium adenosine triphosphstase (Na-KATPase) pump activity was measured by potassium(K)-induced relaxation (with or without ouabain) following precontraction with 10-7 M noradrenaline.The KATP channel was studied by measuring the relaxation response to cromakalim,precontracted with either 10-7M noradrenalineor 60mM potassiumchloride(KCl). The Na- k ATPase pump appeared to be inhibited during salt loading. ATPase inactivation was found to be ouabain sensitive but did not seem to affect subsequent K - induced contraction. Cromakalim produced relaxation of noradrenaline precontracted rings frem the control rats; rings from salt-loaded rats showed significantly less relaxtion than control(p<0.05) under similar conditions. During K-induced precontraction, cromakalim produced a weak biphasic response in the control rings-an initial relaxation and then a reversal. Cromakalim produced further contraction of K-induced precontraction in salt-loaded group. The results suggest that ATP-sensitive potassium channels and Na-K ATPase pumps on the vascular smooth muscle membrane may be deactivated in the development of hypertension during salt loading.(AU)

Enzyme activity in paroxysmal nocturnal haemoglobinuria - like red cells

Activities of two membrane enzymes, actylcholinesterase (AChE) and adenosine triphosphatase (ATPase), were studied in a patient with paroxysmal nocturnal haemoglobinuria (PNH), and in PNH-like cells produced by treating normal red cells with 2-aminoethyl isothiouronium bromide. AChE activity was low in the patient with PNH, particularly in the youngest red cells, but ATPase activity of whole blood was normal. AChE activity was decreased in PNH-like red cells, but ATPase activity and the activities of cytoplasmic enzymes were unchanged. These findings indicate that only the superficial part, and not the whole, of the red cell membrane is affected by the PNH lesion (AU)

Microscopic and enzyme histochemical studies on the liver and kidney of rats treated with fulvine, the toxic alkaloidal constituent of crotalaria fulva

Histochemical changes in the liver of rats, treated with the pyrrolizidine alkaloidal constituent of Crotalaria fulva, indicated primarily damage of the hepatic parenchymal cells. The observed differences in activity of enzymes suggested functional inpairment of the cell membrane, mitochondria, endoplasmatic reticulum, and lysosomes in the liver cells. In large doses, fulvine produced a hyaline droplet degeneration in the epithelium of the proximal convoluted tubules of the kidney. Stability of the mitochondrial and changes in activity of the lysosomal enzymes would imply a functional adaptation, rather than primary damage of the epithelium.(AU)