R. L. Baranowski

A new approach to conformationally restricted peptide analogs: Rigid β-bends. 1. Enkephalin as an example

Abstract A means of producing a peptide analogue that is permanently fixed in a β-bend conformation has been devised. These analogues are based on appropriately substituted derivatives of the ring system, 5H-6-oxo-2,3,4,4a,7,7a-hexahydropyrano [2,3,-b]pyrrole. The substituents are chosen to represent the relevant side chains of amino acids. The first analogue of this type of enkephalin has been synthesized and was found to have the same order of magnitude of activity in the guinea pig ileum assay as morphine.

Bicarbonate reabsorption in chronic renal failure studies in man and the rat

Bicarbonate reabsorption during bicarbonate loading was measured in rats and in patients with chronic renal failure (CRF) and in normal human subjects. Bicarbonate reabsorption expressed as Tm/GFR was not significantly different between normal and CRF rats despite the fact that fractional chloride excretion was significantly greater (an indication of volume expansion) in CRF rats than in normals. The ratio of absolute bicarbonate reabsorption/absolute sodium reabsorption, a parameter which corrects for the influence of volume on bicarbonate reabsorption, was significantly higher in CRF rats than in normals. In patients with CRF, bicarbonate reabsorption expressed either as Tm/GFR or as the ratio of absolute bicarbonate reabsorption/absolute sodium reabsorption was not different from that of the normal subjects. In patients with CRF, glomerular filtration rate (GFR) varied between 3 and 47 ml/min. The ratio of absolute bicarbonate reabsorption/absolute sodium reabsorption was inversely and significantly related to GFR, i.e. as nephron mass decreases sodium bicarbonate is preferentially reabsorbed over sodium chloride. These data demonstrate that in CRF bicarbonate reabsorption is enhanced relative to that of sodium and chloride in man.