Chloride fluxes activated by parathyroid hormone in human erythrocytes.

We used the chloride fluorescent probe, 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ), to study chloride fluxes in human erythrocytes. The SPQ load was made by hypotonic buffer (150 mOsm, 10 min). Intracellular fluorescence was monitored continuously at 360 nm excitation and 410 nm emission wavelengths.

Erythrocyte voltage-dependent calcium influx is reduced in hemodialyzed patients.

Background: Uremia displays increased cytosolic free calcium ([Ca2+]i) in many different cell types, supporting the hypothesis of an altered Ca2+ transport modifying the functional activity of calcium signaling pathway.

Methods: Thirty-five hemodialyzed patients and 20 age-matched subjects were studied. Erythrocyte resting [Ca2+]i and Ca2+ influx were measured by the fluorescent Ca2+-sensitive dye fura-2.

Characterization of voltage-dependent calcium influx in human erythrocytes by fura-2.

Thus far, the methods used to determine erythrocyte Ca2+ influx have not allowed the assessment of the kinetics of ion uptake. To overcome this drawback, we studied a new method, using the fluorescent Ca2+-chelator fura-2, which directly quantifies intracellular Ca2+ changes in human erythrocytes. This method has the advantage over previous techniques that it monitors continuously cellular Ca2+ levels.

Association between plasma membrane (Ca+Mg) ATPase and calpain/calpastatin system in rat erythrocytes.

We studied the activity of plasma membrane (Ca+Mg)ATPase from erythrocytes of Milan hypertensive rat strain (MHS) and Milan low calpastatin rat strain (MLCS), that show an activity level of the specific calpain inhibitor, calpastatin, about five fold reduced in comparison with the Milan normotensive rat strain (MNS), while the protease activity level is similar. This imbalance of calpain:calpastatin ratio leads to a decrease of the erythrocyte plasma membrane (Ca+Mg)ATPase activity and to the appearance of 124 kDa fragments, which are the typical products of proteolytic calpain action on the 136 kDa (Ca+Mg)ATPase native form.

(Ca+Mg)ATPase and calcium influx in erythrocytes of patients with idiopathic hypercalciuria.

Increased erythrocyte (Ca+Mg)ATPase activity was previously observed in idiopathic hypercalciuria. In order to verify if this alteration is a primary or a secondary event, we studied Sr influx in erythrocytes from subjects with idiopathic hypercalciuria. (Ca+Mg)ATPase activity was significantly higher in hypercalciuric than in hypercalciuric than in normocalciuric subjects whereas no difference in Sr influx was found between the two groups.