Proximal Luminal Diameters and Cell Volume in Rats Anesthetized with Inactin and Amytal

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Abstract
Luminal diameters and cellular area oi cross‐sectioned, superficial proximal convolutions were measured in freeze‐dryed cryo‐sections of normal, non‐diuretic rat kidneys instantly frozen with liquid nitrogen at the end of clearance‐and micropuncture experiments. Two series were investigated; in one series rats were anesthetized with the thiobarbiturate Inactin; in the other series the oxybarbiturate Amytal was used as anesthetic; all other factors were equal. In rats anesthetized with Amytal proximal luminal radius was about 14 μm independent of the inulin clearance (ClIN) over a range between 0.57 and 1.61 ml · min‐1· g KW‐1. Proximal cellular volume, as estimated from the cross‐sectional area, was also independent of the clearance value. In the Inactin series proximal luminal radius correlated with ClIN(p ˜ 0.018) The luminal radius was depressed from a value of 14.5 μm at a ClINabout 1.40 ml · min‐1g KW‐1to 12.0 μm at a ClINof about 0.50 ml · min‐1g KW‐1, a value significantly less than that of the Amytal series. Although the cross‐sectional cellular area tended to increase at low clearance values in the Inactin series, the increase was not statistically significant. The data do not exclude, however, the existence of an inverse relationship between cellular volume and ClIN