Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice

OBJECTIVE : The aim of the present study was to evaluate the effects of ovariectomy on the secretory apparatus of natriuretic peptides in right atrial cardiomyocytes. METHODS: Nine-month-old mice underwent bilateral ovariectomy or sham surgery. The blood exam of the ovariectomized mice showed results consistent with castrated females. Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age). Fragments of the right atrium were collected and prepared for electron microscopy examination. The following variables were quantified: the quantitative density and area of the natriuretic peptide granules, the relative volume of euchromatin in the nucleus, the number of pores per 10 μm of the nuclear membrane and the relative volumes of the mitochondria and Golgi complex. RESULTS: The cardiomyocytes obtained from ovariectomized mice indicated that the quantitative density and the area of secretory granules of natriuretic peptides were significantly lower compared with the sham-operated mice. Furthermore, there was a decrease in the relative volume of euchromatin, a lower density of nuclear pores, and lower relative volumes of the mitochondria and Golgi complex in the ovariectomized mice compared with the sham-operated mice. These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides. CONCLUSION: A lack of estrogen caused hypotrophy of the secretory apparatus in right atrial cardiomyocytes that could explain the weak synthesis of natriuretic peptides in mice. Furthermore, one of the mechanisms of blood pressure control was lost, which may explain, in part, the elevated blood pressure in ovariectomized mice. .

El péptido auricular natriurético en las disfunciones tiroideas

Las disfunciones tiroideas están asociadas con cambios en la concentración del péptido auricular natriurético (ANP)

Correlation between ANP concentrations in atria, plasma and cerebral structures and sodium chloride preference in Wistar rats

We determined whether ANP (atrial natriuretic peptide) concentrations, measured by radioimmunoassay, in the ANPergic cerebral regions involved in regulation of sodium intake and excretion and pituitary gland correlated with differences in sodium preference among 40 Wistar male rats (l80-220 g). Sodium preference was measured as mean spontaneous ingestion of 1.5 per cent NaCl solution during a test period of 12 days. The relevant tissues included the olfactory bulb (OB), the posterior and anterior lobes of the pituitary gland (PP and AP, respectively), the median eminence (ME), the medial basal hypothalamus (MBH), and the region anteroventral to the third ventricle (AV3V). We also measured ANP contens in the right (RA) and left atrium (LA) and plasma. The concentrations of ANP in the OB and the AP were correlated with sodium ingestion during the preceding 24 h, since an increase of ANP in these structures was associated with a reduced ingestion and vice-versa (OB: r = -0.3649, P<0.05; AP: r = -0.3291, P<0.05). Moreover, the AP exhibited correlation between ANP concentration and mean NaCl intake (r = -0.4165, P<0.05), but this was not the case for the OB (r = 0.2422. This suggests that differences in sodium preference among individu male rats can be related to variations of AP ANP level. Earlier studies indicated that the OB is involved in the control of NaCl ingestion. Our data suggest that the OB ANP level may play a role mainly in day-today variations of sodium ingestion in the individual rat.

Presence and release of immunoreactive atrial natriuretic peptide (ANP) in Bufo arenarum spermatozoa after HCG treatment

Atrial natriuretic peptide (ANP)-like immunoreactivity has been demonstrated in mature spermatozoa of Bufo arenarum. However, after spermiation induced by Gonadotropin Releasing Hormone (GnRH), no ANP immunoreactivity was detected in testicular spermatozoa. Recently, the presence of GnRH and GnRH receptors in amphibian testes has been demonstrated. To clarify if the loss of ANP-like immunoreactivity in spermatozoa is a direct effect of GnRH or pituitary gonadotropins, a study on Bufo arenarum adult males, has been performed. The in vivo treatment with Human Chorionic Gonadotropin (HCG) induced spermiation and loss of ANP-like immunoreactivity. The in vitro treatment with HCG showed the same results. However, in vitro GnRH treatment failed to cause spermiation and loss of ANP-like immunoreactivity. The present results indicate that ANP from mature spermatozoa is regulated via gonadotropic hormones and may be involved in the spermiation process.

Cellular localization of atrial natriuretic peptide and tissue kallikrein in the human hypothalamus

In the kidney, renal atrial natriuretic peptide (ANP) is considered to play an important role wter and salt homeostasis. Immunoreactive ANP in the brain of lower invertebrates, such as the rat, has been shown to be localizaed in the hypothalamus and septum. Several studies have investigated the possibility of a regulatory system in the brain similar to that of the kidney. Since neuronal function is acutely sensitive to disturbances of the intracranial water and salt balance we have attempted to immunolocalize ANP-containing cells in the normal human hypothalamus, using a polyclonal antiserum specific to ANP. Also, we have observed tissue kallikrein (TK), using a polylonal antiserum specific to TK, in the same areas as ANP. A regulatory role for TK on prolactin has been suggested as the rationale for the co-localization of these two hormones in human prolactinomas. Therefore, it could be suggested that TK plays a similar role in the processing of precursor ANP in the brain. It is contemplated to examine the status of these peptides in patients with cerebral oeodema

Atrial natriuetric factor levels in Liver cirrhosis in Upper Egypt

Atrial natriuretic factor [ANF] has been shown to have a potent natriuretic, diuretic and vasodilating effects in several species. Previous studies have indicated abnormal levels in alcoholic cirrhosis. Therefore, we found it worthwhile to study its levels in Upper Egyptians with liver cirrhosis. The study included a total of 20 subjects with liver cirrhosis, 10 with and 10 without ascites complicating the disease together with 7 completely healthy subjects with comparable age who served as controls. ANF levels were significantly increased in subjects with cirrhosis compared with controls and in patients with ascites compared with those without ascites. The elevations were marked and present in all cirrhotic subjects taking mean + 2 S.Ds. of control levels as the upper limit of normal levels. These findings are strongly suggesting that reduced sensitivity to the renal effects of ANF lead to renal sodium retention, progressive intravascular volume expansion and atrial distention with further increased secretion of ANF. These effects are especially marked in ascitic patients

Plasma atrial natriuretic peptide concentrations during the normal menstrual cycle in healthy volunteers

This study investigated whether the concentration of atrial natriuretic peptide [ANP] changes during the normal menstrual cycle and whether the changes parallel the known fluctuation of aldosterone and female sex hormones or not. Plasma ANP concentrations rose from 19.83 +/- 9.56 [range 10-58 pg/ml] in the menstrual phase to 24.94 +/- 17.21 [range 10-81 pg/ml] in the follicular phase [p = 0.1605] and decreased to 15.04 +/- 8.74 [range 5.8-44 pg/ml] in the luteal phase [p = 0.0067] in 30 normal menstruating healthy volunteers. The reduced level of ANP in the luteal phase could be a compensatory response to the natriuretic effect of the increased progesterone. Aldosterone value was highest when ANP value was lowest

Changes of circulating atrial natriuretic peptide at vaginal delivery in women with essential hypertension

To examine the influence of vaginal delivery in hypertensive pregnancy on atrial natriuretic peptide [ANP], its concentrations were determined by radioimmunoassay technique in 30 pregnant women with established essential hypertension and 10 comparable healthy pregnant controls, during late pregnancy, labor and immediately after vaginal delivery. Plasma ANP levels were increased from 198.96 +/- 16.9 pg/ml during late pregnancy to 228.28 +/- 20 pg/ml during labor and 276.97 +/- 8.7 pg/ml immediately after vaginal delivery in women with essential hypertension. These differences are statistically significant. A positive correlation between ANP and mean arterial pressure is demonstrated