No abstract

The expression of renin and angiotensinogen genes and their proteins were studied daring the progression of diabetes using adult BioBreeding spontaneously diabetic rats at 1 day and 2-12 months of diabetes. The number of renin-stained cells per juxtaglomerular apparatus was determined by immunocytochemistry. Initially, at 2 months of diabetes the number of renin-stained cells per juxtaglomerular apparatus increased significantly (p< 0.0001,2 months versus resistant groups) and was followed by a decrease in the number and intensity of renin-stained cells after 12 months of diabetes (/>=0.007, 2 months versus 12 months). A significant negative correlation was observed between the number of renin-containing cells and the duration of diabetes (r=0.99,p=0.014). Immunoreactive angiotensinogen was restricted to the proximal tubule and appeared increased after 4 and 8 months of diabetes as compared with the 2-and 12-month diabetic groups. Renin messenger RNA (mRNA) levels increased with the onset of diabetes and decreased markedly during chronic diabetes. At 1 day of diabetes, renin mRNA levels were 700% higher than at 12 months of diabetes. Angiotensinogen mRNA levels were unchanged. We conclude that diabetes results in an initial increase in renin gene expression, and as the duration of diabetes lengthens, there is a progressive decrease in renin gene expression and in the number of cells containing renin. These findings suggest that as the duration of diabetes and the age of the animal lengthens, there is a decrease in the number of cells expressing the renin gene. Physiological studies using the streptozocin rat model have suggested that the altered glomerular hemodynamics, namely, increased glomerular capillary pressure and decreased ultrafiltration coefficient, seen in diabetes are responsible for subsequent glomerular injury and decreased renal function.3 Angiotensin converting enzyme inhibition corrects the glomerular hemodynamic changes observed in diabetes and may arrest the progression of glomerular damage and renal

SynopsisA series of novel, functionalized catecholamines (congeners) has been synthesized in which, formalistically, the N-isopropyl group of isoproterenol has been extended by a linear alkyl chain of varying length, terminated by a carboxyl group. Model amide derivatives have also been prepared in order to optimize the biological activity of these derivatives and also to aid in the design of appropriate peptides for the synthesis of conjugates. As a result of these studies, a series of amino acid and monodisperse peptide carriers, containing p-aminophenylalanine as the point of attachment for the drug, was prepared, together with the corresponding conjugates. In uitro and in uiuo evaluation of the congeners, model amides, and conjugates has demonstrated that the biological activity of these derivatives is extremely sensitive to structural modifications a t a point far-removed from the pharmacophore, in both the congener amide and conjugate series. A number of the model amides and conjugates have proven to he highly active when tested in both in uitro and in uiuo test systems. The implications of these results in terms of a novel structure-activity approach to drug design are discussed.

A series of functionalized catecholamines (congeners) has been synthesized in which, formalistically, the N-isopropyl group of isoproterenol has been extended by a linear alkyl chain of varying length, terminated by a carboxy group or a substituted amide. The compounds were prepared generally via the reductive amination of norepinephrine with a keto acid or a preformed keto amide. An alternate synthesis of the model amide derivatives, involving activation of the carboxylic acid congeners and coupling with amines, was complicated in the case of short-chain derivatives by facile cyclization to lactams. In vitro evaluation of these compounds as potential beta-adrenergic agonists has shown that, while the carboxylic acid congeners have relatively low potencies, the model amide derivatives have potencies that are highly dependent on both the length of the alkyl chain and also the nature of the substituent on the amide. In general, aromatic amides are the most potent, although the nature and position of substituents on the aromatic group dramatically influences their potency. The implications of these studies, in terms of general beta-adrenergic drug design and also the attachment of the carboxylic acid congeners to carriers, are discussed.