Spontaneous contractions in elasmobranch vessels in vitro

Area of Science:

• Cardiovascular Physiology
• Comparative Anatomy
• Marine Biology

Background:

• Spontaneous contractions (SC) are crucial for vascular function, but their presence and regulation in elasmobranchs remain largely unexplored.
• Elasmobranchs, a group of cartilaginous fishes, exhibit unique physiological adaptations.
• Understanding vascular dynamics in these species offers insights into vertebrate cardiovascular evolution.

Purpose of the Study:

• To investigate the occurrence and characteristics of spontaneous contractions (SC) in isolated blood vessels of four elasmobranch species.
• To determine the influence of contractile agonists and environmental factors like hypoxia on SC.
• To compare SC patterns across different vessel types and species, correlating findings with their swimming behaviors.

Main Methods:

• Isolated vessel preparations from yellow stingray, clearnose skate, ghost shark, and spiny dogfish.
• Assessment of spontaneous contractions in dorsal aortas, ventral aortas, ductus Cuvier, and hepatic portal veins.
• Pharmacological manipulation using contractile agonists, epinephrine, and indomethacin.
• Exposure to hypoxic conditions and high potassium chloride (KCl) concentrations.

Main Results:

• SC were observed in unstimulated dorsal aortas of stingray and ghost shark.
• Agonist-induced SC appeared in ventral aortas of stingray and skate, and ductus Cuvier of stingray.
• Hepatic portal veins of dogfish exhibited rhythmic SC, with altered frequency under hypoxia and complete inhibition by KCl.
• KCl demonstrated unusual inhibition of both SC and resting tone in dogfish hepatic portal veins.

Conclusions:

• Spontaneous contractions are a prevalent feature in diverse elasmobranch vascular beds.
• The propensity for SC may correlate with elasmobranch swimming behaviors.
• The unusual response of dogfish hepatic portal veins to KCl suggests unique vascular smooth muscle properties in this species.