THE REGULATION OF PH IN RESISTANCE ARTERIES FROM SPONTANEOUSLY HYPERTENSIVE AND WISTAR-KYOTO RATS - THE EFFECT OF BICARBONATE

Objective: To assess intracellular pH regulation in the presence of bi carbonate in resistance arteries from spontaneously hypertensive rats and Wistar-Kyoto (WKY) rats. Methods: Intracellular pH was determined in isolated resistance arteries from male adult SHR and WKY rats with the pH-sensitive fluorescent dye bis-carboxyethyl carboxyfluorescein, while the arteries were mounted in a myograph for simultaneous measure ments of force. The arteries were acid-loaded using the ammonium chlor ide technique and the recovery from the acidosis was determined in res ting arteries and in arteries activated with 50 mmol/l potassium or ar ginine vasopressin. This protocol was performed in the presence and in the absence of bicarbonate. Results: In the absence of bicarbonate th e intracellular pH was higher in resting arteries from SHR than in tho se from WKY rats, whereas during activation no significant difference was found. In the presence of bicarbonate no difference in intracellul ar pH between arteries from SHR and WKY rats could be found. The addit ion and washout of 15 mmol/l ammonium chloride were associated with la rge force transients in activated arteries both from SHR and from WKY rats. The proton recovery rate at intracellular pH 6.85 in the absence of bicarbonate was higher in activated arteries from SHR than in thos e from WKY rats, whereas in resting arteries no significant difference was found. In the presence of bicarbonate no significant difference b etween SHR and WKY rat arteries was found. Conclusion: In the presence of bicarbonate a possible abnormality of the sodium-hydrogen exchange in resistance arteries from SHR is not manifested, because regulation of intracellular pH by bicarbonate-dependent mechanisms can compensat e for such an abnormality.