Gastrin/cholecystokinin type B receptors in the kidney: molecular, pharmacological, functional characterization, and localization

Abstract

Background Gastrin/cholecystokinin type B receptors (CCKBRs) can be found on parietal cells and smooth muscle cells and are the predominant brain CCK receptors. Recent cloning studies indicate that this receptor type might also be expressed in the kidney. Materials and methods We used Northern blot analysis in guinea pig. kidney and reverse transcriptase polymerase chain reaction (RT‐PCR) in several murine kidney cell lines to evaluate this organ for the expression of the CCKBRs. The receptor was pharmacologically characterized by displacement experiments using [125I]‐BH‐CCKs and various agonists and antagonists. Polyclonal antibodies vs. the CCKBRs were raised in chicken, and immunohistochemistry on tissue sections was used to localize the receptor within the organ. The effect of gastrin on renal cell growth was measured using proximal tubulus (MCT) cells, which were cultured with gastrin (10−9 M) for 24–72 h. Cell counts and [3H]‐thymidine incorporation experiments were performed. Results CCKBR transcripts can be detected in kidney RNA (tubules > glomeruli > interstitium). RT‐PCR revealed CCKBR transcripts in proximal tubules (MCT cells) and in mesangium (MMC). The medullary thick ascending limb of Henle's loop and several control tissues such as liver and muscle were negative. Displacement experiments using [125I]‐BH‐CCK and various agonists and antagonists identified binding sites with typical CCKBR pharmacology. CCKBRs were localized in the proximal tubulus, distal collecting ducts and mesangium cells. Treatment of rested MCT cells with gastrin 17‐1 induced cell proliferation and [3H]‐thymidine incorporation by at least 40% compared with normal growth (P < 0.05). Conclusion These results show for the first time that CCKBRs are present in selected areas of the kidney, and strongly confirm our previous observation that this organ expresses binding sites for [125I]‐gastrin. Furthermore, gastrin might act as a growth factor in the kidney.

Renal Toxicity of Radiolabeled Peptides and Antibody Fragments: Mechanisms, Impact on Radionuclide Therapy, and Strategies for Prevention

“…However, an excess of unlabeled octreotide may also interfere with binding of 111 In-octreotide to other receptors such as megalin. Expression of cholecystokinin 2 and glucagonlike peptide 1 receptors on proximal tubular cells was described (20,21), and many other ligand-specific receptors may be expressed in the kidneys. The importance of these receptors for the renal uptake of radiolabeled peptides remains to be determined.…”

Cholecystokinin and Gastrin Receptors

“…CCK2R, expressed in the rat kidney on tubules and collecting ducts, mediates changes in renal potassium and sodium absorption (546). The role of gastrin as a growth factor has been proposed due to its ability to induce proliferation of a renal cell line (121,497). Surprisingly, impact of CCK2R invalidation on these effects was not explored in knockout mice.…”

Expression of the cholecystokinin 2-receptor in normal human thyroid gland and medullary thyroid carcinoma

“…The sections were incubated with 3% H 2 O 2 for 20 min to block endogenous peroxidase activity followed by incubation in 5% swine normal serum. The sections were incubated with specific primary antibodies (anti-calcitonin IgG from rabbit (DAKO A0576; DAKO, Hamburg, Germany); anti-human CCK 2 R IgY from chicken (13,14)) for 48 h at 4 8C in a moist chamber at dilutions between 1:30 and 1:1280. After washing three times with PBS, the sections were incubated with anti-rabbit IgG from swine (DAKO) or anti-chicken IgY (Dianova, Hamburg, Germany) at a dilution of 1:50 for 1 h at 22 8C.…”