Acid/base may be more variable than previously thought

Acid-base regulation, alpha-stat, and the emperor's new clothes

Considerable time and effort have been expended to determine the most appropriate technique for management of a patient's acid-base status during hypothermic cardiopulmonary bypass. A critical question is whether to maintain plasma pH at 7.4 regardless of temperature (pH-stat) or to permit a relative alkalosis as the patient is cooled (alpha-stat). Until recently, there has been a remarkable lack of evidence in the literature for a consistent physiological benefit provided by one protocol over the other. The alpha-stat versus pH-stat controversy has taken on the characteristics of the emperor's new clothes, with alpha-stat winning by default because of theoretical arguments and because it was technically easier to perform. Part of the explanation is the realization that cellular mechanisms are capable of maintaining intracellular pH despite fluctuations in extracellular conditions. The prevailing plasma pH does have strong influence over cerebral blood flow, even to the point of overriding normal autoregulatory mechanisms. Recent evidence suggests that cerebral blood flow variations between alpha-stat and pH-stat conditions have important implications for patient outcomes.

The alternative splicing pattern of the tenascin-C pre-mRNA is controlled by the extracellular pH

Alternative splicing of primary transcripts is an ubiquitous and reversible mechanism for the generation of multiple protein isoforms from single genes. Here we report that in cultured normal human fibroblasts, small pH variations of the culture medium (from 7.2 to 6.9) strikingly modify the alternative splicing pattern of the tenascin-C primary transcript. Since such extracellular pH variations occur in many normal and pathological conditions, microenvironmental pH may be an important element for the regulation of RNA alternative splicing in vivo.

A possible explanation for growth hormone resistance in chronic renal failure

Perhaps the liver in renal failure significantly alters its pH in order to attempt to maintain homeostasis. This alteration might explain the growth hormone resistance found in children with chronic renal failure.

Diseased cells and pH

Diseased cells may alter their intracellular pH. This could explain such diverse activities as resistance to hormones, resistance to medications, and preferential metastasis to the same locations.