Effects of hypothyroidism on jejunal mucosal function: study by in situ luminal perfusion in rats.
To assess the effects of hypothyroidism (HT) on small-intestinal function, HT was induced in rats (120-150 g) by methimazole in drinking water. After 6 wk of methimazole, intestinal absorption studies were performed in HT and in control (C) rats by in situ luminal perfusion of a 20-cm proximal jejunal loop with a bicarbonate buffer containing sodium, glucose or fructose, glycine or lysine, and phenol red as a nonabsorbable marker for determination of water fluxes. Mucosa from the perfused segment was taken for assay of disaccharidases and ATPases and for light and electron microscopy. Compared with C rats, HT rats had significantly lower jejunal transport rates of water (2.54 +/- 0.36 versus 5.02 +/- 0.7 microL/min/microgram mucosal protein, p < 0.03), sodium (37.1 +/- 10.3 versus 102.7 +/- 18.6 mumol/min/microgram protein, p < 0.05), and glucose (1.49 +/- 0.28 versus 5.17 +/- 0.82 mumol/min/microgram protein, p < 0.02). A reduction in glycine transport was also observed but did not attain statistical significance (p = 0.058). Fructose and lysine transport was unchanged. Mucosal sucrase and lactase activities were similar in both groups, but Na,K-ATPase was significantly lower in HT rats (1.17 +/- 0.3 versus 4.03 +/- 1.5 mumol inorganic phosphate/h/mg protein; p < 0.05), with a diminution of ouabain binding sites by 41.5%. Light microscopy of jejunal mucosa from HT rats did not differ from that from C rats; electron microscopy showed mild mitochondrial swelling in HT enterocytes. A group of HT rats were treated with L-thyroxine during 4 wk; these rats had absorption rates, mucosal enzyme activities, ouabain binding, and mucosal morphology not different from C rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Pediatrics, Rambam Medical Center, Haifa, Israel.
M
M
Berant
E
E
Diamond
W
W
Mabriki
O
O
Ben-Yitzhak
D000818:Animals; D001693:Biological Transport, Active; D001834:Body Water / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007037:Hypothyroidism / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000473:pathology / Q000503:physiopathology; D007583:Jejunum / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008713:Methimazole; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D008713:Methimazole; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose