Effects of apamin on α-adrenoceptor-mediated changes in plasma potassium in guinea-pigs

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Abstract
1 An intravenous K+-sensitive electrode has been used to monitor plasma [K+] changes induced by adrenaline (1.4–6.8 μg kg−1) and amidephrine (14–340 μg kg−1) in anaesthetized guinea-pigs. 2 A biphasic response consisting of an initial increase in [K+] followed, within 1 min, by a fall below baseline was observed with both agonists. 3 Apamin (0.4–40 μg kg−1) reduced the hyperkalaemic phase of the response to amidephrine in a dose-related, non-competitive manner. The response to adrenaline was also reduced but to a lesser extent. 4 Apamin caused little or no reduction of the hypokalemic phase of the response to either agonist.