Cerebral artery K(ATP)- and K(Ca)-channel activity and contractility: changes with development.

Area of Science:

• Physiology
• Vascular Biology
• Ion Channel Function

Background:

• Cerebral artery contractility regulation differs between fetal and adult states.
• ATP-sensitive (K(ATP)) and Ca(2+)-activated K(+) channels (K(Ca)) are key regulators of vascular tone.
• Understanding these differences is crucial for perinatal and adult cardiovascular health.

Purpose of the Study:

• To test the hypothesis that K(ATP) and K(Ca) channels play distinct roles in regulating intracellular calcium ([Ca(2+)](i)) and vascular tone in fetal versus adult cerebral arteries.
• To elucidate the specific contributions of K(ATP) and K(Ca) channels to norepinephrine-induced responses in sheep middle cerebral arteries (MCA).

Main Methods:

• Simultaneous measurement of vascular tension and intracellular calcium ([Ca(2+)](i)) in ovine fetal and adult MCA.
• Utilized selective K(+) channel openers (pinacidil, NS 1619) and blockers (glibenclamide, iberiotoxin).
• Administered norepinephrine (NE) to induce vascular responses and assessed effects of channel modulators.

Main Results:

• In fetal MCA, K(ATP) and K(Ca) channel activation significantly inhibited NE-induced tension with a modest decrease in [Ca(2+)](i).
• In adult MCA, channel activation reduced tension without significantly altering [Ca(2+)](i).
• K(Ca) channel blockade increased tension and [Ca(2+)](i) in both fetal and adult MCA; K(ATP) blockade did not.

Conclusions:

• K(ATP) and K(Ca) channels are vital for regulating vascular tone in both fetal and adult cerebral arteries, but their impact on intracellular calcium differs.
• In fetal arteries, both channel types modulate L-type calcium channel flux, affecting vascular tone.
• Differences in K(+) channel activity contribute to the distinct contractility regulation observed between fetal and adult cerebral arteries.