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

Abstract

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. Purkinje type-II fibers resemble working ventricular cardiocytes. Both cell types harbor a large paranuclear Golgi complex. The subendocardial Purkinje network is also made up of these two cell types. In this location, Purkinje type-I fibers form cable-like structures while Purkinje type-II fibers are either located beneath the former or abut directly on the endocardium. The latter are not separated from adjacent working ventricular cardiocytes by connective tissue septa. Coronary arteries and arterioles, as in birds, are surrounded by a cushion of Purkinje type-II fibers which blend with the surrounding myocardium. These results indicate that, in the rat, the entire intraventricular conduction system is constituted of endocrine cells producing ANF.

Immunodetection of α1E Voltage-gated Ca2+ Channel in Chromogranin-positive Muscle Cells of Rat Heart, and in Distal Tubules of Human Kidney

“…First, the distribution of anti-␣1E-positive cells in heart closely resembles the distribution of chromogranin A/B, which is co-localized with ANP (Steiner et al 1990). Second, cardiac peptide hormones such as ANP are widely expressed in the conducting system of rat (Cantin et al 1989), bovine Forsgren 1993,1995), and human (Benvenuti et al 1997). They are detected in atrial and ventricular walls (Toshimori et al 1988).…”

Atrial natriuretic factor in Purkinje fibers of rabbit heart.

“…In the rat, the intracavitary Purkinje fibers are of two types: one that resembles atrial cardiocytes (Purkinje type I) and another that is more akin to ventricular cardiocytes (Purkinje type II). 15 Both types contain a much greater number of secretory granules harboring irANF and a much larger Golgi complex. The results of the present study indicate that, in the rabbit, the Purkinje fibers are of only one type, as already described, 23 the number of secretory granules containing irANF is much smaller, and the Golgi complex is less elaborate.…”

The presence of ANP in rat peritoneal mast cells

“…However, the uncleaved proANP also is released into blood and circulates together with the mature ANP [18]. The presence of proANP (1-126, 16.9 kDa), but not of the mature ANP (99-126, 2.5 kDa) was shown in the extracts of rat atrium tissues [3]. In the rat peritoneal mast cells, we have revealed the presence of two ANP-immunoreactive proteins.…”

“…The content of the atrial granules is released under effect of overload, oxygen deficiency, and many other physiological and pathological processes in myocardium. ANP is also produced by ovine fibroblasts infiltrating the myocardial infarct [2], by cells of rat [3] and bovine [4] heart conductive system, neurons of the rat brain [5], cells of the rat thymus [6], cells of the bovine cornea [7], rat vascular smooth muscle cells [8], and murine macrophages [9].…”