Hirofumi Kurose

Intranasal absorption of salmon calcitonin

SummaryEight normal subjects and 4 children with osteogenesis imperfecta were administered salmon calcitonin (S-CT) intranasally, and the phamacokinetics of S-CT were studied. In the normal subjects, the plasma S-CT concentration showed a dose-dependent increase over a dosage range of 200–400 IU. Maximal plasma concentrations were reached 20–60 min after intranasal administration of S-CT. The plasma calcium concentration was significantly decreased 60 min after the administration. In the children. S-CT was also absorbed through the nasal mucosa. This suggests that nasal spraying may be an efficient method for administration of S-CT.

Cooperation of synthetic insulin-like growth factor I/somatomedin C and 1,25-dihydroxyvitamin D3 on regulation of function in clonal osteoblastic cells.

We investigated the effects of insulin-like growth factor I/somatomedin C (IGF-I/SM-C), and the interaction of IGF-I and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on mouse clonal osteoblasts, MC3T3-E1. IGF-I stimulated [3H]thymidine incorporation into the DNA of the cells at concentrations of 1.3-130 X 10(-9) M. The alkaline phosphatase (ALP) activity in cultures was also raised by the hormone at the same concentrations. The optimal dose of IGF-I was 13 X 10(-9) M. Co-addition of IGF-I (1.3-130 X 10(-9) M) and 1,25(OH)2D3 (10(-11) to 10(-10) M) to the culture of MC3T3-E1 cells caused a synergistic increase in ALP activity. 25(OH)D3 and 24,25(OH)2D3 showed a similar effect with IGF-I at 1000-2000 times higher concentrations than 1,25(OH)2D3. [3H]Proline incorporation into collagenase digestible protein (CDP) in media was stimulated dose-dependently by IGF-I up to 2.2-fold over the control levels at 130 X 10(-9) M. Addition of 1,25(OH)2D3 (5 X 10(-11) M) and IGF-I further elevated the proline incorporation into CDP. However, the increment in CDP synthesis, induced by the two hormones was less than the increment in ALP activity. Thus, we conclude (1) that IGF-I stimulates both cell replication and differentiated functions in cultured murine osteoblasts and (2) that IGF-I and 1,25(OH)2D3 have the synergistic effect on ALP activity and the additive effect on collagen synthesis in MC3T3-E1 cells.

Effect of single oral phosphate loading on vitamin D metabolites in normal subjects and in X-linked hypophosphatemic rickets

There have been several reports that document abnormal vitamin D metabolism in X-linked hypophosphatemic rickets (XLH). Those reports indicate a blunted renal 25-hydroxyvitamin D-1 alpha-hydroxylase response to a potent stimulator, phosphorus restriction. We examined here its response to phosphate supplementation. Seven normal volunteers and 12 patients with XLH were submitted to single oral phosphate loading. This treatment produced a marked elevation of the serum phosphorus level, with a mild reduction in the serum calcium level. In normal subjects, although the concentrations of intact parathyroid hormone and mid-region parathyroid hormone were increased, with two peaks at 2 and 8 h after treatment, there were no significant changes in vitamin D metabolites including 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D (24,25(OH)2D) and 1,25-dihydroxyvitamin D (1,25(OH)2D). On the other hand, in the patients with XLH, the serum 1,25(OH)2D level increased from 23.4 +/- 12.0 (mean +/- SD) pg/ml to 44.3 +/- 33.6 pg/ml 6 h after ingestion without any significant change in 25(OH)D or 24,25(OH)2D.

Microcarriers facilitate mineralization in MC3T3-E1 cells

SummaryMC3T3-E1 cells showed mineral deposits after about 1 week of culture when incubated in the presence of microcarrier beads. These deposits appeared as white spots on the dish surface, and under light microscopy the cells showed multiple cell layers and mineralization around the microcarriers. The deposits stained positive with calcium-specific Von Kossas method. Using conventional assay, alkaline phosphatase activity (ALP) and parathyroid hormone-stimulated intracellular cAMP production were lower in the microcarrier cultures than in the control, but using cytochemical methods, high alkaline phosphatase activity was found around the microcarriers. These results indicate that microcarriers facilitated the formation of multiple cell layers and provided a culture environment for mineralization.

Treatment of renal osteodystrophy in children with 1αOHD3 and 24, 25(OH)2D3

Three pediatric patients with renal osteodystrophy were treated with 1αOHD3 and 24, 25(OH)2D3. While serum calcium level significantly decreased, no significant effects were found on serum phosphorus, alkaline phosphatase, parathyroid hormone and urinary excretion of calcium. These results suggest that 24, 25(OH)2D3 may play some roles in bone and mineral metabolism.