Transforming growth factor beta 1 increases the number of apoptotic bodies and decreases intracellular pH in isolated periportal and perivenular rat hepatocytes.
Transforming growth factor beta 1 (TGF beta 1) is involved in promoting cell death by apoptosis in the liver, whereas the activation of Na+/H+ exchanger has been related to cell proliferation. The aim of this study was to gain information on the effects of TGF beta 1 on intracellular pH and Na+/H+ exchange activity in isolated periportal (PP) and perivenular (PV) rat hepatocytes using the pH-sensitive dye BCECF in a perfused subconfluent hepatocyte monolayer. Steady-state intracellular pH (pHi) in a bicarbonate-free solution (HEPES) were 7.17 +/- 0.031 in PP and 7.15 +/- 0.041 in PV cells. Treatment with TGF beta 1 (120 pmol/L) for 7 hours increased the number of apoptotic bodies by 25% and 38%, and decreased steady-state pHi to 7.11 +/- 0.018 (P = .05) and to 7.07 +/- 0.021 (P < .02), respectively, in PP and PV hepatocytes. In HEPES, cells recovered from an acid load, extruding protons at a rate (JH) of 4.85 +/- 1.01 mmol/L/min in PP cells and of 4.91 +/- 0.99 mmol/L/min in PV hepatocytes. This recovery appeared amiloride inhibitable (1 mmol/L). Culture with TGF beta 1 for 7 hours induced (in HEPES) a decrease of pHi recovery rate from an acid load more in PV (by 46%) than in PP hepatocytes (by 35%, P < .05). Acute administration of epidermal growth factor (EGF) (10 to 100/mL) induced an increase in Na+/H+ exchange activity by 32% and 27%, respectively, in PP and PV cells compared with controls. In contrast, in cells cultured for 7 hours with 120 pmol/L TGF beta 1, the acute administration of EGF slightly increased Na+/H+ exchange activity (by 18%, P < .05) only in PP cells. This study demonstrates that pHi and Na+/H+ exchange activity are decreased by TGF beta 1, which increases the number of apoptotic bodies in periportal and perivenular rat hepatocyte primary cultures.
Benedetti
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A
Clinica di Gastroenterologia, University of Ancona, School of Medicine, Italy.
Di Sario
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A
Svegliati Baroni
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G
Jezequel
A M
AM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D005452:Fluoresceins; D005456:Fluorescent Dyes; D016212:Transforming Growth Factor beta; D004815:Epidermal Growth Factor; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein