Cellular localization of calcium, heavy metals, and metallothionein in lobster (Homarus americanus) hepatopancreas.

This investigation combines confocal microscopy with the cation-specific fluorescent dyes Fluo-3 and BTC-5N to localize calcium and heavy metals along the length of intact lobster (Homarus americanus) hepatopancreatic tubules and isolated cells. A metallothionein-specific antibody, developed in mollusks with cross-reactivity in crustaceans, showed the tissue-specific occurrence of this metal-binding protein in several organ systems in lobster and in single cell types isolated from lobster hepatopancreas. Individual lobster hepatopancreatic epithelial cell types were separated into pure single cell type suspensions for confocal and antibody experiments. Intact hepatopancreatic tubules showed high concentrations of both calcium and heavy metals at the distal tips of tubules where mitotic stem cells (E-cells) are localized. In addition, a concentrated distribution of calcium signal within isolated single premolt E-cells in solution was disclosed that might suggest an endoplasmic reticulum compartmentation of this cation within these stem cells. Both E- and R-cells showed significantly (P < 0.05) greater intracellular calcium concentrations in premolt than intermolt, suggesting the accumulation of this cation in these cells prior to the molt. Antibody studies with lobster tissues indicated that the hepatopancreas possessed 5-10 times the metallothionein concentration as other lobster organ systems and that isolated E-cells from the hepatopancreas displayed more than twice the binding protein concentrations of other cells of this organ or those of blood cells. These results suggest that crustacean hepatopancreatic stem cells (E-cells) and R-cells play significant roles in calcium and heavy metal homeostasis in this tissue. Interactions between the four hepatopancreatic cell types in this regulatory activity remain to be elucidated.

Remodeling of rat neonatal pulmonary artery: role of matrix metalloproteinases.

We studied whether rapid thinning of large pulmonary arteries of neonatal rats is associated with breakdown of collagen. Pulmonary artery extracts from fetal to 21 days of age were assayed for collagen content and matrix metalloproteinases. Within 3 days postpartum, no changes in collagen content, collagenolytic activity, or levels of stromelysin-l or gelatinase A were observed. After day 3, collagen content and total proteolytic activity increased with little change in matrix metalloproteinase expression. Thus, collagen was not degraded, and the late increases in collagen and total proteolytic activity were probably growth related. Unlike adult rats in which collagen is broken down after reversal of hypoxic pulmonary artery remodeling, collagen is not broken down in neonatal pulmonary arteries during adaptation to extrauterine life.

Hormonal and renal responses to water drinking in moderately trained and untrained humans.

Endurance exercise training alters the regulation of body fluids. To investigate specifics of these alterations, hormonal, electrolyte, and renal responses to water ingestion (1% of lean body wt) were studied in six moderately trained (T) and 6 untrained (UT) male subjects. No differences between groups for base-line hormonal, electrolyte, or renal measurements were found. After water ingestion, atrial natriuretic factor remained unaltered in both groups. Predrink plasma antidiuretic hormone (ADH) levels of 0.51 +/- (SE) 0.19 (UT) and 0.47 +/- 0.07 microU/ml (T) remained unchanged in the T group but were reduced from min 9 through 90 in the UT group. At 30 min postdrink, UT subjects had lower ADH values than T subjects (0.18 +/- 0.02 vs. 0.33 +/- 0.05 microU/ml), while plasma osmolality was similarly reduced by approximately 3 mosmol/kg in both groups. Urine flow rates increased in both groups from similar values of 0.85 +/- 0.24 (UT) and 0.67 +/- 0.11 ml/min (T) to peak flows of 4.6 +/- 1.6 for UT and 2.7 +/- 1.1 ml/min (T) to peak T, P less than or equal to 0.05) at 60 min postdrink. Urine osmolality was reduced from similar values of 809.1 +/- 62.1 and 867.0 +/- 56.1 mosmol/kg to values of 248.8 +/- 87.6 and 469 +/- 146.1 mosmol/kg for UT and T, respectively (UT vs. T, P less than 0.05), at 60 min. Reduced ADH before reductions in plasma osmolality in the UT but not the T subjects suggests that T subjects have a reduced oropharyngeal inhibition of ADH.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal and vascular fluid responses to maximal exercise in trained and untrained males.

The trained condition is associated with alterations in fluid regulation. In attempt to elucidate mechanisms responsible for these differences, resting, postexercise (maximal treadmill exercise of 8-13 min duration), and recovery measurements were made in seven trained (mean peak O2 consumption was 60.5 +/- 1.6 ml.kg-1.min-1) and seven untrained (mean peak O2 consumption was 40.7 +/- 1.7 ml.kg-1.min-1) male subjects. Samples were obtained by venipuncture with subjects seated. No significant differences in resting plasma osmolality (Osm), sodium, potassium, antidiuretic hormone (ADH), aldosterone, renin activity, or atrial natriuretic factor were found between groups. Maximal exercise produced significant increases in all of the above variables. Values immediately postexercise were similar between groups except for plasma Osm and sodium, which were significantly higher in the untrained group. Despite a reduction in plasma volume of equal magnitude in both groups, trained subjects demonstrated an increase in vascular proteins and mean corpuscular volume during exercise. This increase in plasma protein may be an important initiating factor responsible for the elevated plasma volume after 1-h recovery from exercise in the trained group. Lastly, similar ADH responses despite lower Osm in trained subjects may indicate that training increases the sensitivity of ADH to osmotic stimulation.