Adenylate cyclase activity in microdissected rat liver tissue: Periportal to pericentral activity gradient

✍ Scribed by Christian Cortinovis; Fritz Klimek; Enrique Nogueira

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 562 KB
• Volume: 18
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.1840180124

✦ Synopsis

Adenylate cyclase activity was measured in microdissected samples from lyophilized cryostat sections of rat liver by means of an improved assay. Livers were obtained from adult Sprague-Dawley rats fasted for 22 hr. Adenylate cyclase activities, basal and those elicited by various agents, were determined in dissected samples from periportal and pericentral regions of the classic liver lobule. In all samples, enzyme activity was strongly stimulated by glucagon, cholera toxin, guanosine-S'-O-(3-thiotriphosphate), sodium fluoride and forskolin. The f3-adrenergic agonist isoproterenol produced very weak, if any, enzyme stimulation. Angiotensin I1 did not inhibit the activity elicited by lithium chloride and G W at high concentrations, and pertussis toxin did not enhance the GTP-stimulated activity. We observed a periportalto-pericentral gradient for basal and agent-stimulated activities. (HEPATOLOGY 1993; 18: 160-164.)

The existence of morphological and functional differences throughout the liver lobule has long been reported. A characteristic differential involvement of distinct regions of the liver lobule in certain pathological processes is likewise largely known. It has been, however, only in the last three decades that functional heterogeneity of liver cells has become more than a curiosity and drawn the attention of an increasing number of investigators. Intense work has been performed with histochemical methods on the distribution of a large number of enzymes in hepatocytes (1-3). It is now clear that some key enzymes in specific metabolic pathways are distributed unevenly in periportal and pericentral (perivenous) regions of the liver lobule, a situation supporting the concept of metabolic zonation of the liver parenchyma. Thus, for example, periportal and pericentral hepatocytes would be preferentially