Increasing contractility through stimulation of alpha 1-adrenoceptors in situ by the endogenous agonist may be an alternative way of inotropic support during heart failure and even more so during beta-adrenoceptor blockade.

The present study was undertaken to develop an improved and stabilized method for isolating cardiomyocytes from perfused rat heart. Different lots of the commercial collagenases used for isolating cardiomyocytes give variable results both with respect to the total cell yield and the percentage of elongated cells obtained. When trypsin was present both before and during collagenase treatment of the tissue, the performance of the collagenases was improved and stabilized, and a high and stable cell yield (7.5 x 10(6) cells per heart), and a high percentage of elongated cells (about 70%) was regularly obtained. The cells possessed alpha 1-adrenergic binding sites with binding properties (Bmax = 43.5 fmol/mg protein and Kd = 125.5 pmol/l) in agreement with values previously reported. The cells were able to respond functionally, as the cellular uptake of 86Rb+ increased by 18% after alpha 1-adrenoceptor stimulation with phenylephrine. These criteria indicate that the cells were well preserved during the isolation procedure.

A sensitive radioimmunoassay (limit of detection 7± 1 fmol per tube) for cyclic AMP (cAMP) based on acetylation of both 3H‐cAMP and unlabeled ligand was developed. Rabbit anti‐cAMP antibodies had an apparent Ka for the acetylated ligand of 2× 1010 l/mol. When the unlabeled ligand only was acetylated an increased sensitivity was obtained without loss of specificity.

No abstract

No abstract