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Biomedical subjects

G Zeballos

Publications and source records attributed to G Zeballos.

7 recordsLinked to original sources
PubMed1990

Dynamics of atrial peptide secretion in the coronary circulation of the conscious dog.

The secretion of atrial natriuretic peptide by the heart is not simply the arterial-coronary sinus concentration difference times coronary blood flow, because only a small fraction of total coronary blood flow passes through the atria. We measured coronary sinus and arterial plasma atrial natriuretic factor (ANF) concentrations and blood flow to each part of the heart using the radioactive microsphere technique. Before acute volume expansion, the arterial-coronary sinus ANF difference was 305 +/- 23 pg/ml and rose to 1,009 +/- 220 pg/ml during volume expansion, whereas total coronary blood flow rose from 167 to 465 ml/min. Atrial blood flow rose from 2.9% to 4.6% of total coronary blood flow during volume expansion. ANF secretion rate increased from 51 to 469 ng/min. When divided by atrial weight, ANF secretion rate increased from 4.0 +/- 0.3 to 56 +/- 12 ng/min/g atrial tissue-in other words, from 0.3% to 3.7% of tissue ANF content each minute. Dividing by atrial blood flow indicated that the concentration of ANF leaving atrial tissue was 10,000 to 29,651 pg/ml, and the additional secretion of ANF was determined by the increase in coronary blood flow. Therefore, at least two mechanisms are responsible for altering coronary sinus ANF and circulating ANF: the release rate from atrial myocytes and the washout via changes in atrial blood flow.

Animals↗
PubMed1989

Relationship between plasma atriopeptin concentration and function in the conscious primate.

The renal actions of atriopeptins (APs) 24, 21 and 28 were examined in the conscious primate, macaca fascicularis. AP-24 increased urine flow rate and sodium excretion 20- and 100-fold, respectively. The circulating form of the atriopeptins, AP-28, had similar, even slightly greater (25%) effects when compared to AP-24. AP-21 on the other hand had dramatically reduced effects, less than 20%, when compared to either AP-24 or AP-28. Infusion of AP-24 resulted in marked increases in plasma immunoreactive AP and in renal function. There were direct, significant linear relations between plasma levels and arterial pressure, heart rate, glomerular flow rate, urine flow rate, sodium and potassium excretion. However, the threshold for these effects was generally higher than expected, i.e., greater than 100 pg/ml. Interestingly, there was a 4-fold greater slope for sodium excretion when compared to other renal functions implying a distinctly different mechanism of action. Whereas, the plasma half-life of the peptide was 2 to 3 min, the biological half-life varied from 6 min for sodium excretion to 10 min for urine flow and potassium excretion. The increased slope for the relationship between sodium excretion and plasma AP concentration and the short half-life for sodium excretion indicate that the change in renal sodium handling is independent of urine flow rate and glomerular filtration rate. There is a direct and linear relationship between plasma peptides and renal function which may imply a cause and effect relationship. This extrapolation may, however, be valid only when plasma peptide levels are elevated markedly.

Animals↗
PubMed1987

Elevated atrial natriuretic peptide after the Fontan procedure.

To assess the response of atrial natriuretic peptide (ANP) to rapidly changing right atrial pressures in vivo, we measured ANP levels in 15 patients undergoing the Fontan procedure and compared them with control levels in nine patients undergoing cardiac surgery for lesions not associated with atrial hypertension. There were no significant differences in preoperative ANP levels: 57 +/- 15 pg/ml for patients undergoing the Fontan procedure, 43 +/- 8 pg/ml for control patients. There was no significant change in ANP during surgery or in the postoperative period in control patients. In contrast, ANP increased significantly to 333 +/- 70 pg/ml (p less than .0025) after establishment of right atrial-pulmonary artery continuity with the Fontan procedure and was related to right atrial pressure, which increased from 5 mm Hg before to 14 mm Hg after the Fontan procedure (p less than .001). There was no significant change in left atrial pressure. During the first postoperative day, ANP levels fell to 141 +/- 34 pg/ml (p less than .01) but later increased to 290 +/- 80 pg/ml (p less than .025), a finding that may suggest depletion of a readily releasable intracellular pool of ANP before mobilization of a storage pool. There was no direct relationship between ANP levels and effusions in patients undergoing the Fontan procedure. Pharmacologically significant increases in ANP occur in patients undergoing the Fontan procedure, correlating with increased right atrial pressures, but the relationship between ANP and the fluid derangements after the procedure remains unclear.

Atrial Natriuretic Factor↗
PubMed1975

Alterations during the estrous cycle in the responsiveness of the pituitary to subcutaneous administration of synthetic LH-releasing hormone (LHRH).

To further evaluate the alterations in responsiveness of the pituitary to synthetic LHRH during the proestrous discharge of gonadotropins, LHRH was given SC in the hope of producing a release of FSH as well as LH, and blood samples were removed prior to and at various intervals after the injections of the neurohormone while the rats were anesthetized with tribromoethanol. The procedure of anesthesia and blood sampling produced small declines in both FSH and LH, but these only achieved significance in the case of FSH on the morning of estrus and diestrus day 2. An increase in plasma LH occurred in response to LHRH at all stages of the estrous cycle but was minimal during diestrus. The increment in plasma LH was already increased by 9 AM on proestrus and the titer remained elevated for 2 h. A further increase in response to LHRH occured at 2 PM associated with an increase in initial plasma LH. The maximum response occurred at 5 PM together with maximal initial plasma LH, and the characteristics of the response changed such that there was a much larger increase in plasma LH at 20 min and a rapid decline thereafter, so that the response became pulselike. Initial plasma LH had already declined significantly by 9 PM, and this was associated with a dimished pulselike release of LH in response to LHRH. By the morning of estrus, an even smaller pulse-like release occurred. Significant FSH release in response to LHRH occurred at all stages of the cycle as indicated by the increments in plasma FSH. The relative increase in plasma titers was much less than that for LH and responsiveness to LHRH did not increase until 5 PM on proestrus. Responsiveness had already begun to decline by 9 PM on proestrus and by the morning of estrus was similar to that obtained on diestrus. Initial plasma FSH titers were first elevated by 2 PM on proestrus and they remained elevated on the morning of estrus. The results indicate that maximal responsiveness to LHRH in terms of LH release is associated with the proestrous discharge of LH, but that the maximal responsiveness in terms of FSH release terminates long before the endogenous release of hormone ceases sometime on estrus. The increased responsiveness in terms of LH release may be related to prior estrogen secretion and to the priming action of endogenous LHRH. The continued release of FSH in the face of a return of responsiveness to LHRH to low levels indicates that release of FSH on late proestrus and early estrus is not caused by endogenous release to LHRH.

Animals↗