Sex steroids effects on guinea pig airway smooth muscle tone and intracellular Ca2+ basal levels

- Dehydroepiandrosterone and testosterone reduce airway smooth muscle tone and b[Ca2+]i.
- 17β-estradiol barely reduces tracheal basal tone.
- L-VDCC and TRPC3 channels are involved in TES-induced effects.
- Only L-VDCC is involved in 17β-estradiol effects.
- Airway smooth muscle tone and b[Ca2+]i are maintained by L-VDCC and TRPC3 channels.

Testosterone (TES), other androgens and female sex steroids induce non-genomic rapid relaxing effects in airway smooth muscle (ASM). In guinea pig ASM, basal tension was relaxed by dehydroepiandrosterone (DHEA) and TES; 17β-estradiol (E2) had a small effect. Blockers of L-type voltage dependent Ca2+ channel (L-VDCC, D-600) and store operated Ca2+ channel (SOC, 2-APB) also relaxed the basal tone. In tracheal myocytes, DHEA and TES diminished intracellular basal Ca2+ concentrations (b[Ca2+]i) as D-600+2-APB but to a higher extend. TES after D-600+2APB or Pyr3, a blocker of canonical transient receptor potential 3 (TRPC3), further decreased b[Ca2+]i rendering this response equal to TES alone. With indomethacin, the b[Ca2+]i decrease induced by the blockade of L-VDCC and TRPC3 was not changed by the addition of TES. PGE2 or forskolin addition after D600+2-APB, decreased b[Ca2+]i resembling TES response. An adenylate cyclase inhibitor followed by D-600+2-APB lowered b[Ca2+]i, TES showed no further effect. Carbachol-induced [Ca2+]i increment was reduced by TES or DHEA. 17β-estradiol diminished KCl-induced contraction and, in tracheal myocytes, the voltage-dependent inward Ca2+ current. Conclusion: DHEA and TES diminish ASM tone and b[Ca2+]i by blocking L-VDCC and probably a constitutively active TRPC3, and by PGE2 synthesis. E2 lowers ASM basal tone by blocking only L-VDCC.