C L Sears | PubMed Health

PubMed1992

AIDS enteropathy.

Chronic diarrhea is one of the hallmarks of advanced human immunodeficiency virus (HIV) disease. The symptoms of this complication are troublesome, have a significant impact on the patient's quality of life, and in severe cases can lead to extreme abnormalities in fluids and electrolytes and can even cause death. The workup for AIDS-associated diarrhea is often frustrating and frequently unrewarding. However, during the last 10 years, much has been learned about the causes of diarrhea; while treatment is still often ineffective, some advances have been made. Dr. John G. Bartlett and his colleagues in the Department of Medicine at Johns Hopkins University School of Medicine have been responsible for many of these advances. In this AIDS Commentary, these experts discuss recent advances that have enhanced our understanding of chronic diarrhea in HIV-infected persons and offer their recommendations for the most efficient and effective approach to managing these patients.

AIDS-Related Opportunistic Infections↗

PubMed1992

Regulation of intestinal guanylate cyclase by the heat-stable enterotoxin of Escherichia coli (STa) and protein kinase C.

The heat-stable enterotoxin of Escherichia coli (STa) stimulates membrane-bound guanylate cyclase in intestinal epithelium and induces fluid and ion secretion. Using the T84 human colon carcinoma cell line as a model, we observed that phorbol esters markedly enhanced STa-stimulated cyclic GMP accumulation in T84 cells (C. S. Weikel, C. L. Spann, C. P. Chambers, J. K. Crane, J. Linden, and E. L. Hewlett, Infect. Immun. 58:1402-1407, 1990). In this study we document that the phorbol ester treatment increases 125I-STa-binding sites as well as membrane-bound guanylate cyclase activity in T84 cells and provide evidence that both effects are mediated by phosphorylation. Guanylate cyclase activity was increased approximately 50% in membranes prepared from intact T84 cells treated with phorbol-12,13-dibutyrate (beta-PDB) and after treatment of homogenates with beta-PDB in a manner dependent on ATP, MgCl2, and cytosol. Similarly, treatment of membranes with purified bovine brain protein kinase C in the presence of appropriate cofactors and beta-PDB resulted in an increase in STa-stimulated guanylate cyclase activity of about 70%. Likewise, the number of 125I-STa-binding sites was increased by about 25 to 40% in membranes prepared from intact cells or homogenates treated with beta-PDB; no effect on binding affinity (Kd = 0.15 nM) was noted. These experiments suggest that protein kinase C may phosphorylate the STa receptor-guanylate cyclase or a closely related protein and increase guanylate cyclase activity. The stimulatory effects of protein kinase C on STa-sensitive guanylate cyclase are opposite in direction to the profound inhibitory effects of the kinase on atrial natriuretic peptide-stimulated guanylate cyclase, demonstrating differential regulation by protein kinases within the guanylate cyclase-receptor family.

Adenosine Triphosphate↗