Immuno-electron microscopy of atrial natriuretic factor secretory pathways in atria and ventricles of control and cardiomyopathic hamsters with heart failure.

The secretory pathways of atrial natriuretic factor have been investigated in atrial and ventricular cardiocytes of control and cardiomyopathic Syrian hamsters in severe congestive heart failure with four antibodies: a monoclonal antibody (2H2) against rat synthetic atrial natriuretic factor (101-126), which is directed against region 101-103 of rat atrial natriuretic factor (99-126), and polyclonal, affinity-purified antibodies produced in rabbits against synthetic C-terminal atrial natriuretic factor (101-126), synthetic N-terminal atrial natriuretic factor (11-37) or the putative cleavage site of atrial natriuretic factor (98-99): atrial natriuretic factor (94-103). Application of the immunogold technique on thin frozen sections (immunocryoultramicrotomy) revealed an identical picture with the four antibodies. In atria of both control and cardiomyopathic hamsters where atrial natriuretic factor secretion is regulated, the atrial natriuretic factor propeptide travels, uncleaved, from the Golgi complex to immature and mature secretory granules.

Processing of the atrial natriuretic factor propeptide by atrial cardiocytes as revealed by immunocryoultramicrotomy.

Antibodies were raised against three fragments of the rat ANF molecule: C-terminal atrial natriuretic factor (ANF)-(101-126), N-terminal ANF-(11-37), and the putative cleavage site of the ANF propeptide, ANF-(94-103). These antibodies were purified by affinity chromatography and revealed a major band (17K) corresponding to the propeptide by Western blot analysis. Antibodies against ANF-(94-103) were used in a RIA.

Atrial natriuretic factor in Purkinje fibers of rabbit heart.

The Purkinje fibers of the rabbit false tendons (chordae tendineae spuriae) are endocrine cells containing immunoreactive atrial natriuretic factor (ANF) and ANF messenger RNA (mRNA). These cells, as visualized by immunocryoultramicrotomy, contain immunoreactive ANF in their secretory granules and their Golgi complex and exhibit ANF mRNA, as visualized by in situ hybridization with an ANF complementary RNA probe. The content of immunoreactive ANF and ANF mRNA of the Purkinje fibers is midway between that of atrial and ventricular working cardiocytes.

Desensitization of the stimulatory A2 adenosine receptor-adenylate cyclase system in vascular smooth muscle cells from rat aorta.

We have previously shown that adenylate cyclase present in rat aorta vascular smooth muscle cells can be stimulated by adenosine, its analogs and other agonists. In the present studies, we have examined the effect of preexposure of aorta vascular smooth muscle cells to N-ethylcarboxamide adenosine (NECA) on adenylate cyclase activity stimulated by NECA and other agonists. The vascular smooth muscle cells, when exposed to NECA, resulted in a concentration- and time-dependent loss of NECA-stimulated adenylate cyclase activity.

Atrial natriuretic factor in the impulse-conduction system of rat cardiac ventricles.

A complex network of atrial natriuretic factor-producing cells has been delineated by biochemical and morphological techniques in the rat ventricular myocardium. The chordae tendineae spuriae (CTS; false tendons) contain ANF mRNA and the ANF propeptide (Asn 1-Tyr 126) as assessed by Northern blot analysis, high-pressure liquid chromatography and immunohisto- and -cytochemistry, using three different affinity-purified antibodies: monoclonal and polyclonal antibodies against C-terminal ANF (Arg 101-Tyr 126) and polyclonal antibodies against N-terminal ANF (Asp 11-Ala 37). Two types of cells harboring ANF-containing secretory granules constitute the CTS: the majority (Purkinje type I) have ultrastructural similarities with both atrial and classical Purkinje fibers.