T-type Calcium Channels in Arterial Smooth Muscle: Activity, Regulation and Function

Voltage-gated Ca2+ channels (CaV) are key regulators of excitation-contraction coupling in arterial smooth muscle. Despite evidence of T-type CaV channels in rodent smooth muscle, little is known of their regulation and function. This thesis sought to delineate T-type Ca2+ channels, ascertain if they are regulatory targets of vasoactive signaling pathways, and to reveal their function in arterial smooth muscle. Experiments progressed from cells to whole animals, and employed an integrative range of techniques such as electrophysiology, pressurized myography, intravascular catheterization, polymerase chain reaction, western blotting and computational modeling. Using patch clamp electrophysiology and defined pharmacology, T-type currents were successfully separated from L-type, and further divided into components mediated by specific subtypes (i.e. CaV3.1 and CaV3.2). In rat cerebral arteries, T-type channel activity was shown to be a regulatory target of vasodilatory kinases. In particular, β-adrenergic receptors and downstream activation of protein kinase A selectively inhibited CaV3.2 currents. Nitric oxide additionally suppressed CaV3 channels through protein kinase G signaling. Subsequent work on rat and mouse arteries revealed an unanticipated function for CaV3.2 in arterial tone development. In particular, we identified a novel feedback response mediated by CaV3.2, whereby it triggered ryanodine receptors to release Ca2+ sparks that consequently activate the large conductance Ca2+-activated K+ channel to hyperpolarize and relax arteries. While the majority of the experimental work was conducted in animals, access to human brain tissues provided the opportunity to translate our foundational observations. Indeed, human findings revealed for the first time the presence of three distinct CaV subtypes in cerebral arterial smooth muscle and that each subtype uniquely orchestrates arterial tone development and blood flow. In conclusion, this thesis revises our knowledge on Ca2+ handling in arterial smooth muscle by describing a novel paradigm in which T-type channels either facilitate or counteract arterial tone development.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Discipline thesis:degree_discipline

Cardiovascular & Respiratory Sciences

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2015

Author dc:creator

• Harraz, Osama Fathalla

Advisor dc:contributor.advisor

• Welsh, Donald

• Physiology
• Biophysics
• Pharmacology

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

eng

DOI

http://dx.doi.org/10.11575/PRISM/28530

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:11023/2127