Stimulation of arteriolar number by salbutamol in spontaneously hypertensive rats

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Abstract
.beta.2-Adrenergic involvement in arteriolar development in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats was studied. Newly weaned 20 day WKY and SHR rats were injected with salbutamol, a selective .beta.2-agonist (50 .mu.g/day s.c. plus 5 mg/100 ml in drinking water), for 20 days. At 40 days, under 2% chloralose-7.5% urethan anesthesia (6 ml/kg), the cremaster muscle was prepared for in vivo microscopy to estimate the number and diameter of open arterioles, or the arterioles were injected with latex to determine the total number of arterioles and their maximal diameters. Control SHR had 62% (P < 0.01) fewer open arterioles and a 32% (P < 0.001) reduction in the total number of arterioles compared to WKY controls. Salbutamol stimulated 67% (P < 0.001) and 22% (P < 0.05) increases in total number of the smallest arterioles in the SHR and WKY, respectively. Salbutamol significantly reduced the maximum diameter of latex-injected arterioles. Apparently the decreased arteriolar density in the cremaster muscle of SHR rats may result from differences in the .beta.-adrenergic mechanism.