Calmodulin in normal and cystic fibrosis human intestine at different developmental stages

Immunoreactive calmodulin in cystic fibrosis kidneys

BACKGROUND

Microscopic nephrocalcinosis has been detected at autopsy in 35 of 38 (92%) cystic fibrosis (CF) patients. A primary defect of calcium metabolism in the kidney has been postulated. Intracellular calcium and calmodulin (a calcium binding protein) have been shown to be increased in CF tissues.

AIMS

To determine whether CF kidneys obtained at autopsy contain normal amounts of calmodulin and whether the presence of immunoreactive calmodulin correlates with nephrocalcinosis.

METHODS

An immunoperoxidase method was used to stain kidneys obtained from six CF individuals aged three to 27.5 years (mean 15.75 +/- 10.2 years) and five individuals who died of chronic debilitating disease aged eight to 17 years (mean 13.6 +/- 3.9 years). Calcium staining was undertaken using the von Kossa (silver precipitation) and Alizarin red methods.

RESULTS

No quantifiable difference in immunoreactive calmodulin staining was demonstrated in autopsy renal specimens between six CF patients and five chronically diseased controls. Three of six CF patients aged 22.8 +/- four years and two of five chronically diseased controls aged eight to 16 years respectively had detectable immunoreactive calmodulin staining. Within the CF group the presence of microscopic nephrocalcinosis did not correlate with immunoreactive calmodulin staining.

CONCLUSION

This study does not support the premise that a calmodulin-dependent defect of intracellular calcium handling contributes to the microscopic nephrocalcinosis seen in CF.

Calmodulin content and activity in normal and coeliac duodenum

Calmodulin is an important modulator of intracellular calcium processes and may be implicated in the calcium malabsorption of coeliac disease. The calmodulin content in extracts of duodenal biopsy specimens from 48 normal control subjects and 28 patients with coeliac disease was determined. Radioimmunoassay was used to measure immunoreactive calmodulin while a cyclic adenosine 3',5'-monophosphate phosphodiesterase activity assay was used to measure biologically active calmodulin. Calmodulin values measured by both assays were similar for control and disease groups. Mean (SEM) immunoreactive calmodulin values were 1.68 (0.09) micrograms/mg protein for controls and 1.67 (0.15) and 1.45 (0.15) micrograms/mg protein for partial and total villous atrophy respectively. These values were not significantly different. Biologically active calmodulin values were 2.77 (0.21), 1.82 (0.34), and 3.24 (0.33) micrograms/mg protein for control, partial, and total villous atrophy subjects respectively. The biologically active calmodulin values in the partial villous atrophy group were significantly lower than in controls and total villous atrophy subjects. In the phosphodiesterase assay, the calmodulin antagonist trifluoperazine inhibited the activity stimulated by purified calmodulin and by the extracts to the same extent. These results show that calmodulin values are normal in coeliac disease and provide no evidence that changes in calmodulin account for the abnormal calcium absorption in these patients.

Expression of membrane receptors and (proto)oncogenes during the ontogenic development and neoplastic transformation of the intestinal mucosa

The functional relationship between membrane receptors involved in signal transduction and (proto) oncogene expression has been explored during the ontogenic development and differentiation of the intestinal mucosa in man and rat. The present review develops detailed picture of the current understanding of some mechanisms underlying growth and function of normal, immortalized and cancerous intestinal epithelial cells.

Expression of brush border calmodulin-binding proteins during human small and large bowel differentiation

The expression and immunocytochemical localization of three brush border cytoskeletal calmodulin-binding proteins, caldesmon, fodrin, and the 110 kDa subunit of the 110 kDa calmodulin complex, have been studied in human intestinal epithelial cells as a function of their ontogenic differentiation. At immature stages (fetal week 8), caldesmon and fodrin were present in undifferentiated intestinal epithelial cells. However, no 110 kDa protein was detectable except a 135 kDa immunoreactive species. The 110 kDa form appeared at week 12, when microvilli differentiate, and became prominent at week 14 simultaneously with the disappearance of the 135 kDa species. Finally at week 14, the calmodulin-binding protein pattern was identical to that found in adults. Immunocytochemical experiments revealed that at week 8, antibodies to caldesmon and fodrin gave a fluorescence lining at the periphery of the cells, whereas the 110 kDa immunoreactive species was hardly detectable. Then, as early as week 12 of gestation, with the three antisera, a bright fluorescence lined the apex of the cells, as in adults. In the colon, the events were delayed. This study demonstrates that the developmental pattern of the three calmodulin-binding proteins investigated, caldesmon, fodrin and the 110 kDa subunit, parallels the temporal differentiation of human intestinal brush borders and the proximo-distal morphological intestinal maturation.