Presence and interaction in tissues of atrial natriuretic peptide, oxytocin and vasopressin: new insights.

Atrial natriuretic peptide, oxytocin and vasopressin are three well known and widely studied molecules since many years. They have been fully characterised from a genetic and biomolecular point of view and a number of receptor-dependent functions have been recognised for them. Nevertheless, in the last years our group has conducted morphologic studies, using an immunohistochemical approach complemented by molecular biology techniques, and could show non-canonical localization and co-localization of these peptides in normal and pathologic tissues, that permitted us to postulate that they may be involved in a wider range of functions than usually assumed and not yet fully understood. In this minireview we summarise some of the main results that open new scenarios in the comprehension of the biologic activities of these peptides and allow to postulate a role for them as diagnostic tools.

Modifications of atrial natriuretic peptide and vasopressin peptides in the rat hypothalamic supraoptic nucleus during resistance training.

Many studies have demonstrated the involvement of atrial natriuretic peptide (ANP) and vasopressin (VP) in the homeostasis of body fluids, but few studies have regarded the hypothalamic magnocellular neurosecretory system during physical exercises. The aim of the present immunohistochemical work is to study the activity of ANP and VP secreting neurons of the hypothalamic supraoptic nucleus during and after resistance training. The study was carried out in Wistar rats trained by a physical resistance-type exercise, using a rung ladder and a varying load fastened to the tail of each rat; the exercise lasted 20 min everyday for periods of 15, 30 and 45 days. Animal groups were sacrificed at the end of each training period and one group was sacrificed after 60 days from the beginning of training, i.e.15 days after completing a 45 day training. The results show that ANP and VP-immunopositivity is at first lesser in the trained rats than in the corresponding controls and then increases from the 15th to the 45th day of training; the increase of the immunopositivity in the trained rats indicates a decreased degranulation of the neurons. The comparison between VP and ANP-immunopositivity suggests that in the early phase of training VP-release in the bloodstream is higher than ANP-release, therefore the antidiuretic action of VP is expected to prevail on ANP action and an electrolyte unbalance may occur.

Anatomical and clinical study on effects of sonography with pulse inversion and microbubble contrast in rabbit kidney.

Aim of the present study was to evaluate by transmission electron microscope (TEM) modifications in rabbit kidney-parenchyma after submission to ultrasound contrast agent (UCA) with Pulse Inversion Harmonic Imaging (PIHI). Seven inbred male albino rabbits were divided into three groups: 1) control group (n = 1 animal); 2) sonicated group (n = 3 animals); 3) sonicated group with UCA injection (CEUS) (n = 3 animals). The first group was not exposed to ultrasonography (US) and/or UCA. The second and third groups underwent baseline US and later to US with PIHI with a high mechanical index; in the third group UCA was simultaneously administered. Ultrastructural studies and image analysis were blindly performed on 50 samples (2mm3), including cortex and medulla, by two experienced pathologists with TEM. By TEM observations of the first and second groups showed no structural modifications of renal cortex and medulla. TEM observations of the third group showed ultrastructural changes of renal corpuscle, proximal and distal convoluted tubules and collecting tubules; further in the most of observed sections the filtration membrane had an alteration of typical trilaminar pattern and vacuolisation of glomerular endothelial cells with irregular edges. Therefore in rabbit kidney submitted to CEUS some ultrastructural modifications were observed.

ANP presence in the hypothalamic suprachiasmatic nucleus of developing rat.

In previous research, we studied both the oxytocin and vasopressin ontogeny in the hypothalamic supraoptic and paraventricular nuclei, and the ANP-ontogeny in the hypothalamic supraoptic nucleus. In this paper we evaluate the ANP-ontogeny in the rat hypothalamic suprachiasmatic nucleus; infact the suprachiasmatic nucleus it is known to synthesize vasopressin, a peptidic hormone involved in the homeostasis of the body fluids by an antagonistic role to ANP. Immunohistochemical techniques show that ANP is present in the hypothalamic suprachiasmatic nucleus of the rat at 18 degrees day of i.u. life and at 0 degrees to 3 degrees day of postnatal life. PCR analysis confirms the ANP-mRNA expression. Thus, it is possible to adfirm that the suprachiasmatic nucleus is a synthesis site of ANP, and ANP appears in both the supraoptic and suprachiasmatic nuclei at the same developmental stage. Moreover, ANP and vasopressin appear at the same developmental stage since both the peptides are involved in the homeostasis of body fluids.

Ultrastructural biologic effects of sonography with pulse inversion and microbubble contrast in rabbit liver.

PURPOSE: This prospective study was conducted to evaluate the biologic effects of microbubble destruction with pulse-inversion harmonic imaging on rabbit liver parenchyma. METHODS: The livers of 6 albino rabbits were examined sonographically by a single investigator. Three rabbits underwent contrast-enhanced sonography, with scanning starting 5 seconds after injection by using pulse-inversion harmonic imaging with a mechanical index of 1.2. Four time-triggered images were recorded at a rate of 1 frame every 2 seconds. For comparison, 3 control rabbits had pulse-inversion harmonic imaging with a mechanical index of 1.2 only, without contrast medium. Immediately after sonography, the animals were killed and uninterrupted, thin serial sections of the liver from both groups were analyzed by energy-filtered transmission electron microscopy. RESULTS: The hepatic parenchyma of rabbits exposed to contrast agents had ultrastructural damage: mitochondria with fragmented crests; interrupted rough endoplasmic reticulum; enlarged intercellular spaces; highly vacuolized cytoplasmic areas; dilated sinusoids, sometimes with an irregular and interrupted endothelial wall; fragmented hepatocyte microvilli in dilated spaces of Disse; fragmented or missing microvilli in bile canaliculi; vacuolated and lysosome-deprived hepatic cytoplasm around the bile canaliculi; markedly injured or fragmented endothelium in larger vessels; and damaged basal membrane. Control-group results indicated that exposure to ultrasound alone did not cause ultrastructural damage to hepatic cells. CONCLUSIONS: Simultaneous exposure to contrast administration and pulse-inversion harmonic imaging with a high mechanical index causes ultrastructural damage in the rabbit liver.