Single-Vesicle Catecholamine Release Has Greater Quantal Content and Faster Kinetics in Chromaffin Cells from Hypertensive, as Compared with Normotensive, Rats

Role of the Endoplasmic Reticulum and Mitochondria on Quantal Catecholamine Release from Chromaffin Cells of Control and Hypertensive Rats

“…This high-resolution technique provides insight on quantitative and qualitative kinetic aspects of the last fusion steps of exocytosis in isolated single chromaffin cells in the millisecond time range (Wightman et al, 1991;Borges et al, 2005). We found that SHR chromaffin cells, stimulated with short pulses of ACh or K ϩ , had a more sustained production of spike secretory events and a drastic augmentation of the quantal catecholamine content of individual secretory vesicles with faster fusion kinetics, compared with normotensive rats (Miranda-Ferreira et al, 2008).…”

“…In trying to clarify the mechanisms involved in the kinetic differences of single-vesicle quantal release of catecholamine between SHR and normotensive rats found in our recent study (Miranda-Ferreira et al, 2008), we felt it of interest to study whether alterations of Ca 2ϩ handling by the endoplasmic reticulum and mitochondria could explain those differences in the exocytotic responses. Here, we present such a study in which we have compared the kinetics of quantal catecholamine release elicited by the following stimuli applied to single chromaffin cells from normotensive and hypertensive rats: 1) pulses of ACh or K ϩ , to favor Ca 2ϩ entry through voltage-dependent Ca 2ϩ channels (Douglas and Poisner, 1961); 2) acute application of a mixture of caffeine, ryanodine, and thapsigargin (CRT) to quickly release the Ca 2ϩ stored in the ER (Cuchillo-Ibáñ ez et al, 2002); 3) acute application of the protonophore FCCP to cause release into the cytosol of Ca 2ϩ accumulated into mitochondria during previous cell stimulations with ACh or K ϩ pulses (Montero et al, 2000); and 4) ACh or K ϩ pulses given after cell treatments with CRT or FCCP.…”

“…We recently performed the first study on the kinetics of single-vesicle secretory events, using a carbon fiber electrode and amperometry in isolated single chromaffin cells from control and SHRs (Miranda-Ferreira et al, 2008). This high-resolution technique provides insight on quantitative and qualitative kinetic aspects of the last fusion steps of exocytosis in isolated single chromaffin cells in the millisecond time range (Wightman et al, 1991;Borges et al, 2005).…”

Functionomics: the analysis of a postgenomic concept on the basis of pregenomic pharmacological studies in smooth muscle

“…We have shown that there is a significant increase of alpha-adrenoceptors in this organ (Caricati Neto et al 1992), a condition which can be related to the increase of blood pressure due to the involvement of arterial smooth muscle. More recently, we have shown for the first time that catecholamine release has greater quantal content and faster kinetics in isolated chromaffin cells of SHR, measured through single vesicle amperometry (Miranda-Ferreira et al 2008). …”

Atypical Ca2+ currents in chromaffin cells from SHR and WKY rat strains result from the deficient expression of a splice variant of the α1D Ca2+ channel

“…Nonetheless, it has been argued that this strain is unsuitable as control studies because of genetic heterogeneity and the high incidence of spontaneous hypertension (20). Our laboratory recently compared the electrophysiological properties of voltage-gated Ca 2ϩ currents (I Ca ) in adrenal chromaffin cells (CCs) from WKY rats and SHR to determine whether the catecholamine hypersecretion reported in CCs from the SHR strain (27,28) was due to an augmented function of voltage-gated Ca 2ϩ channels. Our results showed that the electrophysiological and pharmacological properties of I Ca in adrenal CCs from SHR and WKY are indistinguishable (39), implying that catecholamine hypersecretion in SHR CCs cannot be attributed to augmented Ca 2ϩ entry, and also that the choice of the WKY strain as control was appropriate in this case.…”