Hormone metabolism in the pulmonary circulation

Area of Science:

• Endocrinology
• Cardiovascular Physiology
• Vascular Biology

Background:

• The pulmonary circulation's role in peptide hormone metabolism is not fully understood.
• Hormone levels can be influenced by surgical procedures and anesthesia.
• Hepatic extraction is a primary mechanism for hormone removal, but other sites may exist.

Purpose of the Study:

• To investigate the role of the pulmonary vessel endothelium in hormone metabolism.
• To determine if the pulmonary circulation contributes to the removal of circulating hormones.
• To measure arterial hormone concentrations during aorto-coronary bypass surgery.

Main Methods:

• Blood samples were collected from pulmonary and radial arteries of 117 patients undergoing aorto-coronary bypass surgery.
• Hormonal levels including insulin, glucagon, and others were measured.
• Arteriovenous differences were analyzed to infer hormone degradation in the pulmonary circulation.

Main Results:

• Insulin and glucagon concentrations were significantly higher in pulmonary artery blood compared to radial artery blood.
• No significant differences were observed for growth hormone, prolactin, C peptide, IGF-I, FSH, LH, TSH, PTH, thyroglobulin, T3, T4, fT3, and fT4.
• Elevated prolactin levels were noted, attributed to anesthesia agents (propofol and fentanyl).

Conclusions:

• The pulmonary circulation contributes to the homeostatic removal of insulin and glucagon, removing approximately 9-10% of these hormones.
• The pulmonary vessel endothelium plays a role in the clearance of certain peptide hormones.
• These findings suggest an additional layer of hormonal regulation beyond hepatic extraction.