[Comparison of ultraviolet A and ultraviolet B on 1,25-dihydroxy-vitamin D3 and bone metabolism in ovariectomized rats].

OBJECTIVE

To investigate the effects of ultraviolet A (UVA) and ultraviolet B (UVB) on serum 1,25-dihydroxy-vitamin D3 and bone metabolism of ovariectomized rats and to compare them on bone metabolism.

METHODS

In the study, 40 six-month female Sprague-Dawley rats were randomly divided into sham-operated control group (sham), osteoporosis model group (OVX), UVA irradiation group (OVX+UVA) and UVB irradiation group (OVX+UVB). Except the sham-operated control group, the remaining rats were ovariectomized to establish the osteoporosis models. After the model establishment, the UVA and UVB groups were exposed to UV irradiation with wavelengths of 340 nm and 313 nm, respectively. After the 15-week UV irradiation treatment, bone material density and serum 1,25(OH)2D3, osteocalcin (bone gamma-carboxyglutamic acid protein, BGP), calcium (Ca) and phosphorus (P) contents were measured.

RESULTS

Compared with the sham group, the body weights [(486.5±55.7) g, (488.3±32.1) g, (494.1±49.8) g, vs. (408.6±36.1) g, P<0.01] were significantly higher in the model group, UVA group and UVB group; proximal femur BMD [(0.318±0.025) g/cm(2), (0.316±0.031) g/cm(2), (0.322±0.036) g/cm(2), vs.(0.386±0.027) g/cm(2), P<0.01], central BMD [(0.321±0.038) g/cm(2), (0.319±0.051) g/cm(2), (0.320±0.053) g/cm(2), vs.(0.347±0.044) g/cm(2), P<0.05], distal femur BMD [(0.320±0.028) g/cm(2), (0.318±0.030) g/cm(2), (0.322±0.036) g/cm(2), vs.(0.361±0.046) g/cm(2), P<0.01] were significantly lower in the model group, UVA group and UVB group. After the 15-week treatment of UV radiation, compared with the sham group, proximal femur BMD [(0.162±0.125) g/cm(2) vs.(0.293±0.076) g/cm(2), P<0.01], central BMD [(0.205±0.102) g/cm(2) vs.(0.306±0.031) g/cm(2), P<0.01] , distal femur BMD [(0.153±0.119) g/cm(2) vs.(0.274±0.017) g/cm(2), P<0.01] were significantly decreased in the model group; serum 1,25(OH)2D3 [(19.80±1.67) ng/L vs. (28.35±4.32) ng/L, P<0.01], BGP [(11.00±0.01) ng/L vs.(16.64±0.01) ng/L,P<0.01] and Ca [(2.14±0.10) mmol/L vs.(2.68±0.16) mmol/L,P<0.01] were significantly lower in the model group. Compared with the model group, proximal femur BMD [(0.248±0.092) g/cm(2), (0.218±0.123) g/cm(2), vs.(0.162±0.125) g/cm(2), P<0.01], central BMD [(0.272±0.010) g/cm(2), (0.275±0.036) g/cm(2), vs.(0.205±0.102) g/cm(2), P<0.01] and distal femur BMD [(0.251±0.009) g/cm(2), (0.242±0.063) g/cm(2), vs.(0.153±0.119) g/cm(2), P<0.01] were significantly increased in the UVA group and UVB group; serum 1,25(OH)2D3 [(29.47±4.54) ng/L, (27.56±6.33) ng/L, vs.(19.80±1.67) ng/L, P<0.01], BGP[(15.70±0.01)ng/L, (15.62±0.02) ng/L, vs.(11.00±0.01) ng/L, P<0.01] and Ca [(2.48±0.22) mmol/L, (2.58±0.13) mmol/L, vs.( 2.14±0.10) mmol/L, P<0.01] were significantly higher in the UVA group and UVB group. There were no statistical differences among the UVA group, UVB group and sham group.

CONCLUSION

Both UVA and UVB may improve serum 1,25(OH)2D3 content of ovariectomized rats, promote bone formation, increase bone material density, and relieve bone loss due to osteoporosis.