PH regulation in spread cells and round cells.

M A Schwartz,E J Cragoe,C P Lechene

doi:10.1016/s0021-9258(19)40017-3

Abstract

The aim of this work was to characterize the changes in pH regulation that lead to increased intracellular pH (pHi) in well-spread cells on tissue culture plastic relative to cells on a nonadhesive surface. Bicarbonate was not required for maintenance of a control steady state pHi or of the difference in pHi between round and spread cells. In the absence of bicarbonate, lowering the sodium content of the medium led to decreased pHi and elimination of the difference between round and spread cells. In the presence or absence of bicarbonate, adding ethylisopropyl amiloride lowered pHi and eliminated the difference between round and spread cells. Measurements of recovery from acute acidification in the absence of bicarbonate confirmed that Na+/H+ exchange was enhanced in spread cells. However, recovery from both acidification and alkalinization in the presence of bicarbonate showed that bicarbonate-dependent recovery in both directions, most likely due to sodium-dependent and -independent HCO3-/Cl- exchangers, was also stimulated in spread cells. We conclude that Na+/H+ exchange has a primary role in determining steady state pHi in 3T3 cells in serum and is responsible for the lower pHi in round cells. Bicarbonate-dependent pH regulatory mechanisms are also inhibited in round cells.

Highlights

From the SDepartment of Cellular and Molecular Brigham and Wornens Hospital, and Laboratory and llLansdale, Pennsylvania 19446
The aim of this work was to characterize the changes in pH regulation that lead to increased intracellular pH in well-spread cells on tissue culture plastic relative to cells on a nonadhesive surface
Anchorage-dependent cells were 0.15-0.3 pH units more alkaline when attached to plastic coated with fibronectin or with their endogenous fibronectin-rich extracellular matrix than when in suspension or on a nonadhesive surface, It is important to note that adhesion to tissue culture plastic or other surfaces is mediated by extracellular matrix proteins such as fibronectin or vitronectin [3], which exert their effects through membrane receptors of the integrin family [4]

Summary

Introduction

From the SDepartment of Cellular and Molecular Brigham and Wornens Hospital, and Laboratory and llLansdale, Pennsylvania 19446. In the absence of bicarbonate, lowering the sodium content of the medium led to decreased pHi and elimination of the difference between round and spread cells. In the presence or absence of bicarbonate, adding ethylisopropyl amiloride lowered pHi and eliminated the difference between round and spread cells. Measurements of recovery from acute acidification in the absence of bicarbonate confirmed that Na+/H+ exchange was enhanced in spread cells. Howeve covery from both acidification and alkalinizaticr, ret the presence of bicarbonate showed that bicarbdn in-dependent recovery in both directions, most lik@na@e to sodium-dependent and -independent HC0;/Clyl~ dqangers, was stimulated in spread cells.

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