Milan hypertensive rats
Thick ascending limb of Henle
Springer Online Journal Archives 1860-2000
Abstract Milan hypertensive (MSH) rats develop hypertension around the 3rd–4th week of life and exhibit increased Na-pump activity in adulthood. The present study was performed to evaluate whether or not hypertension is preceded by an increase in Na−K-ATPase activity. Total and ouabain-sensitive ATPase activities were studied in single microdissected medullary thick ascending limb of Henle (mTAL) tubules from MHS, Milan normotensive (MNS) and Sprague-Dawley (SD) rats at 22–24, 26–28 and 45–60 days of age. Data are given as mean±SEM. Total and Na−K-ATPase activity exhibited a developmental pattern in MHS, MNS and SD rats. At 22–24 days no difference was seen between MHS and MNS animals. At 26–28 days MHS had a higher total and Na−K-ATPase activity than MNS (3031+171 vs 2471+178 pmol phosphate/mm tubule per hour,P〈0.05; 2289+205 vs 1653+151,n=10,P〈0.05). At this age there was still no difference in mean arterial blood pressure (88+4 vs 86+3 mm Hg,n=15). Adult MHS rats had higher blood pressure (140+9 vs 112+8 mm Hg,P〈0.001) and higher total (3544+136 vs 2718+215 pmol phosphate/mm tubule per hour,n=10,P〈0.01) and Na−K-ATPase activity (2670+99 vs 1942+217 pmol phosphate/mm tubule per hour,n=10,P〈0.05) than adult MNS rats. We conclude that increased Na−K-ATPase activity in mTAL precedes the development of hypertension in the Milan strain of rats.
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