Sclerosing peritonitis and timolol

Peritoneal sclerosis: one or two nosological entities?

The frequency, pathology, animal models, pathogenesis, clinical manifestations, diagnostic criteria, therapy and prevention of peritoneal sclerosis are reviewed. Many of these aspects have a bimodal configuration which suggests that peritoneal sclerosis, usually considered a single pathology in peritoneal dialysis, is actually two distinct nosological entities: simple sclerosis and sclerosing peritonitis. The former is very frequent, with minor anatomical alterations and low clinical impact; it is reproducible in animals by means of peritoneal dialysis, and is clearly due to the poor biocompatibility of peritoneal dialysis solutions. The latter is rare, with radical anatomical alterations and high mortality requiring valid methods of diagnosis, therapy and prevention; it can only be reproduced in animal models by means other than peritoneal dialysis and seems to be due to factors both related and unrelated to peritoneal dialysis.

Regulation of collagen production by the beta-adrenergic system

The suppression of collagen production by increasing the cyclic (c) AMP content of cultured cells was examined vis-à-vis the beta-adrenergic system. Cultured human fetal lung fibroblasts incubated for 6 h with the beta-agonists isoproterenol or epinephrine produced approximately 30% less collagen per cell than in the absence of the hormones. To demonstrate that the beta-agonists were operating by their interaction with the beta-receptor to stimulate adenylate cyclase to increase the intracellular content of cAMP, d- and l-isoproterenol were incubated separately with the cultured cells. Only l-isoproterenol increased intracellular cAMP and decreased collagen production. While 20 nM l-isoproterenol was effective, the d-isomer was ineffective even at 2muM. An increase in cAMP from 40 to 73 pmol/mg protein was effective in suppressing collagen production; increasing the cAMP content to much higher levels had little additional effect on collagen production. 3-Isobutyl-1-methylxanthine, an analog of theophylline that inhibits phosphodiesterase, potentiated the effect of isoproterenol in suppressing collagen production. Further support for the concept that isoproterenol suppressed collagen production by acting through the beta-receptor was provided by the finding that only the l-isomer of propranolol, a beta-blocker, was effective in blocking both the increase in intracellular cAMP and the suppression of collagen production caused by isoproterenol. These results demonstrate that collagen production in human fibroblasts can be regulated by the beta-adrenergic system and indicate that when the cAMP content is increased beyond a threshold value, collagen production is suppressed. Since collagen production is sensitive to the small changes of cAMP content of cells brought about by beta-stimulation in cultured cells, the results point to a possibly important mechanism for the regulation of collagen production in the body.