Aim: 

The detection of endocannabinoids and corresponding receptors (CB1 and CB2) in several tissues other than nervous system indicates the involvement of these substances in the control of a wide range of physiological activities. Aside from central nervous system, CB1 cannabinoid receptors are also present in the testis, sperm, liver, ovary, muscle, heart, spleen, and pituitary gland. By contrast, CB2 are found mainly in immune cells. However, distribution of CB1 and CB2 receptors in human kidney has not been investigated so far.

Methods: 

An immunohistochemical study of the CB1 and CB2 expression and distribution has been performed in a series of 30 normal human kidneys. Routine samples of adult kidneys were obtained from surgically resected specimens. Fetal kidney tissue was obtained from abortions at different gestational ages.

Results: 

The immunohistochemical profile was constant and highly preserved in fetal and adult kidneys. This pattern consisted on intense cytoplasmic positivities with CB1 and complete negativity with CB2. So, CB1 was diffusely expressed by proximal tubule cells and, selectively, by intercalated cells in the distal nephron. Interestingly, this specific pattern of immunostaining of intercalated cells in the distal nephron was similar to the obtained with the cytokine receptor c-kit (CD117), a distinctive marker of some renal carcinomas.

Conclusion: 

This study describes for the first time the CB1 expression in human renal parenchyma, suggests a role for this receptor in renal physiology, and may be related with some histological types of renal cancer.

Supported by grants from the Jesús Gangoiti- Barrera Foundation and Gobierno Vasco (GIC07/84).