Glomerular dynamics in the hypothyroid rat and the role of the renin-angiotensin system.
Munich-Wistar rats underwent thyroidectomy (TX) with reimplantation of the parathyroid glands. Systemic hemodynamic and micropuncture studies were performed at 1 and 3 wk post-TX, and the results were compared with levothyroxine replaced controls (TXT4). Cardiac output (CO) in TX rats fell progressively and was 40% of that in TXT4 at 3 wk. Renal blood flow declined in parallel with CO. Systemic blood pressure did not fall in TX rats because of a 50% increase in systemic vascular resistance by 3 wk post-TX. Glomerular dynamics were not significantly different between TX and TXT4 rats at 1 wk; however, by 3 wk single-nephron glomerular filtration rate (SNGFR) had fallen to 16.5 +/- 1.1 vs. 34.1 +/- 3.4 nl/min in TXT4 controls (P less than 0.001). In 3-wk TX rats, glomerular plasma flow (QA) was 50.9 +/- 3.7 vs. 108.0 +/- 8.7 nl/min in TXT4 rats (P less than 0.001), net hydraulic ultrafiltration pressure (delta P) was 33 +/- 2 vs. 37 +/- 1 mmHg in TXT4 rats (P less than 0.01), and the ultrafiltration coefficient (Kf) was 0.025 +/- 0.003 vs. 0.084 +/- 0.008 nl X s-1 X mmHg-1 in TXT4 controls (P less than 0.001). Although the changes in systemic and glomerular hemodynamics were progressive over 3 wk, proximal tubular reabsorption fell maximally within 1 wk. Similar patterns of alterations in glomerular dynamics are known physiological consequences of angiotensin II (ANG II).(ABSTRACT TRUNCATED AT 250 WORDS)
Gillum
D M
DM
Falk
S A
SA
Hammond
W S
WS
Conger
J D
JD
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001810:Blood Volume; D007037:Hypothyroidism / Q000473:pathology / Q000503:physiopathology*; D007668:Kidney / Q000187:drug effects; D007678:Kidney Glomerulus / Q000503:physiopathology* / Q000648:ultrastructure; D007684:Kidney Tubules / Q000503:physiopathology; D008297:Male; D009399:Nephrons / Q000187:drug effects; D051381:Rats; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System; D012964:Sodium / Q000378:metabolism
D000804:Angiotensin II; D012964:Sodium; D012083:Renin