Adrenal fasciculata cells express T-type and rapidly and slowly activating L-type Ca²⁺ channels that regulate cortisol secretion

Abstract

Enyeart JJ, Enyeart JA. Adrenal fasciculata cells express T-type and rapidly and slowly activating L-type Ca 2ϩ channels that regulate cortisol secretion. Am J Physiol Cell Physiol 308: C899 -C918, 2015. First published March 18, 2015; doi:10.1152/ajpcell.00002.2015.-In whole cell patch-clamp recordings, we characterized the L-type Ca 2ϩ currents in bovine adrenal zona fasciculata (AZF) cells and explored their role, along with the role of T-type channels, in ACTH-and angiotensin II (ANG II)-stimulated cortisol secretion. Two distinct dihydropyridine-sensitive L-type currents were identified, both of which were activated at relatively hyperpolarized potentials. One activated with rapid kinetics and, in conjunction with Northern blotting and PCR, was determined to be Cav1.3. The other, expressed in approximately one-half of AZF cells, activated with extremely slow voltage-dependent kinetics and combined properties not previously reported for an L-type Ca 2ϩ channel. The T-type Ca 2ϩ channel antagonist 3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2) inhibited Cav3.2 current in these cells, as well as ACTH-and ANG II-stimulated cortisol secretion, at concentrations that did not affect L-type currents. In contrast, nifedipine specifically inhibited L-type currents and cortisol secretion, but less effectively than TTA-P2. Diphenylbutylpiperidine Ca 2ϩ antagonists, including pimozide, penfluridol, and fluspirilene, and the dihydropyridine niguldipine blocked Cav3.2 and L-type currents and inhibited ACTH-stimulated cortisol secretion with similar potency. This study shows that bovine AZF cells express three Ca 2ϩ channels, the voltage-dependent gating and kinetics of which could orchestrate complex mechanisms linking peptide hormone receptors to cortisol secretion through action potentials or sustained depolarization. The function of the novel, slowly activating L-type channel is of particular interest in this respect. Regardless, the well-correlated selective inhibition of T-and L-type currents and ACTH-and ANG II-stimulated cortisol secretion by TTA-P2 and nifedipine establish the critical importance of these channels in AZF cell physiology. adrenal fasciculata; cortisol; ACTH; ANG II; TTA-P2; L-type Ca 2ϩ channel; Cav3.2; Cav1.3 IN MAMMALS, ZONA FASCICULATA cells of the adrenal cortex secrete glucocorticoids in a diurnal rhythm under the control of the pituitary peptide adrenocorticotropic hormone (ACTH) (57). Physical and psychological stress triggers additional bursts of corticosteroid secretion in response to activation of the hypothalamic-pituitary-adrenal axis (57). In some species, including bovine and human, angiotensin II (ANG II) also stimulates glucocorticoid production (10,30,43).Glucocorticoids, including cortisol and corticosterone, regulate a variety of physiological processes, ranging from energy metabolism to long-term memory formation and emotional behavior (8,10,25,32). Chronic excessive cortisol secretion, which occurs in prolonged str...

Role of cAMP/PKA pathway and T-type calcium channels in the mechanism of action of serotonin in human adrenocortical cells

“…Cultured cells did not displayed spontaneous electrical activity (data not shown). As previously demonstrated (Barrett et al, 2016; Enyeart and Enyeart, 2015; Rossier, 2016; Scholl et al, 2015), cultured human adrenocortical cells emitted low-threshold transient inward Ca 2+ currents, identified as T-type currents, in response to increasing depolarizing pulses higher than −60 mV (Fig. 5A).…”

“…Since human adrenocortical cells are known to express different types of membrane Ca 2+ channels (Enyeart and Enyeart, 2015; Felizola et al, 2014; Scholl et al, 2015, 2013), specific Ca 2+ channel blockers have been used to identify the source of Ca 2+ involved in the corticotropic effect of 5-HT. Incubation of cultured adrenocortical cells with the T-type channel blockers mibefradil (10 −6 M) or NiCl 2 at low concentration (8 × 10 −5 M) inhibited the cortisol response to 5-HT by reducing the maximum efficacy and/or potency (Fig.…”

“…In particular, expression of the L-, N- and T-type channels has been documented with a predominant localization in zona glomerulosa. In addition, L- and T-type Ca 2+ currents have been recorded in steroidogenic cells from the glomerulosa and fasciculata zonae (Barrett et al, 2016; Enyeart and Enyeart, 2015, 2013; Payet et al, 1994; Rossier, 2016). Thus, we have hypothesized that 5-HT-induced Ca 2+ influx in adrenocortical cells may be mediated by these channels.…”

Genetic alteration of the metal/redox modulation of Cav3.2 T‐type calcium channel reveals its role in neuronal excitability

“…), hormone secretion (Maturana et al . ; Enyeart & Enyeart, ), neurotransmitter release (Weiss et al . ; Carbone et al .…”

“…Over the last decade, a role of Cav3.2 channels in a variety of physiological functions has been proposed (Huc et al 2009). This includes pain detection and processing (Todorovic & Jevtovic-Todorovic, 2007;Bourinet et al 2014), neuronal excitability and pacemaker activities (Liao et al 2011), hormone secretion (Maturana et al 2009;Enyeart & Enyeart, 2015), neurotransmitter release (Weiss et al 2012;Carbone et al 2014), vascular tone (Hansen, 2015) and fertilization (Bernhardt et al 2015). The Cav3.2-H191Q mouse model will be helpful to decipher a putative role of this Cav3.2 modulation, not only in the physiological processes listed above, but also in a variety of disease states that are thought to rely on altered Cav3.2 activity, such as neuropathic pain, epilepsy, primary aldosteronism and cardiac hypertrophy (Evans & Todorovic, 2015).…”