Phorbol ester increases the dihydropyridine-sensitive calcium conductance in a vascular smooth muscle cell line.
Why the study?
Does phorbol ester increase dihydropyridine-sensitive calcium conductance in A7r5 vascular smooth muscle cells?
Population
A7r5 cultured vascular smooth muscle cell line (n=8 for active phorbol ester experiment)
Comparison
Active phorbol esters: 12-O-tetradecanoyl… vs Inactive phorbol, 4-alpha-phorbol (100 nM)
Design
Preclinical
Authors
Discussion
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Implication
Phorbol esters may modulate VSMC calcium conductance via PKC; leaves open in vivo relevance to human vascular tone.
Key Points
- To identify voltage-dependent calcium conductances in A7r5 vascular smooth muscle cells and determine whether phorbol esters modulate dihydropyridine-sensitive calcium channels.
- Applied the whole-cell voltage-clamp technique with barium as the charge carrier to measure inward currents in cultured A7r5 vascular smooth muscle cells.
- Tested the effects of active phorbol esters (12-O-tetradecanoyl phorbol-13-acetate and phorbol-12,13-dibutyrate) versus an inactive analogue (4-alpha-phorbol) at 100 nM across holding potentials of -80 mV and -30 mV.
- Identified two distinct inward currents: a low-threshold, rapidly inactivating T-type current maximal at -10 mV, and a high-threshold, slowly inactivating L-type current maximal at +10 to +20 mV.
- Treatment with 100 nM 12-O-tetradecanoyl phorbol-13-acetate increased the slowly inactivating L-type current by 32 ± 20% (n = 8, ± SD), an effect replicated by phorbol-12,13-dibutyrate but not by inactive 4-alpha-phorbol.
Structured PICO
Does phorbol ester increase dihydropyridine-sensitive calcium conductance in A7r5 vascular smooth muscle cells?
P
Population
A7r5 cultured vascular smooth muscle cell line (n=8 for active phorbol ester experiment)
I
Intervention
Active phorbol esters: 12-O-tetradecanoyl phorbol-13-acetate (100 nM) and Phorbol-12,13-dibutyrate (100 nM) added to the bath
C
Comparator
Inactive phorbol, 4-alpha-phorbol (100 nM)
O
Outcome
Change in slowly inactivating (L-type) calcium current measured via whole-cell voltage-clamp techniquesurrogate
Phorbol esters acutely modulate dihydropyridine-sensitive calcium conductance in vascular smooth muscle cells, likely via protein kinase C activation.
Cite This Study
Fish et al. (1988) studied this question.