Hill Coefficient Analysis of Transmembrane Helix Dimerization |
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Authors: | Ricky Soong Mikhail Merzlyakov Kalina Hristova |
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Institution: | (1) Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA |
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Abstract: | Sertoli cells are responsible for regulating a wide range of processes that lead to the differentiation of male germ cells
into spermatozoa. Cytoplasmic pH (pH
i
) has been shown to be an important parameter in cell physiology, regulating namely cell metabolism and differentiation. However,
membrane transport mechanisms involved in pH
i
regulation mechanisms of Sertoli cells have not yet been elucidated. In this work, pH
i
was determined using the pH-sensitive fluorescent probe 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF).
Addition of weak acids resulted in rapid acidification of the intracellular milieu. Sertoli cells then recovered pH
i
by a mechanism that was shown to be sensitive to external Na+. pH
i
recovery was also greatly reduced in the presence of 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and amiloride.
These results point toward the action of an Na+-driven HCO3−/Cl− exchanger and/or an Na+/HCO3− cotransporter and the action of the Na+/H+ exchanger on pH
i
regulation in the experimental conditions used. pH
i
recovery was only slightly affected by ouabain, suggesting that the inhibition of Na+/K+-ATPase affects recovery indirectly, possibly via the shift on the Na+ gradient. On the other hand, recovery from the acid load was independent of the presence of concanamycin A, a specific inhibitor
of the V-type ATPases, suggesting that these pumps do not have a relevant action on pH
i
regulation in bovine Sertoli cells. |
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Keywords: | Sertoli cells Intracellular pH Membrane ion transporter 2′ 7′ -Bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein |
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