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Hypertensive cardiac hypertrophy is associated with collagen accumulation in the myocardial interstitium. Myocardial fibrosis accounts for impaired myocardial stiffness and ventricular dysfunction. Although cardiac fibroblasts are responsible for the synthesis of fibrillar collagen, factors that regulate collagen synthesis in cardiac fibroblasts are not fully elucidated. The purpose of this study was to investigate the effect of angiotensin II (Ang II) on collagen synthesis by cultured rat cardiac fibroblasts. A 24-hour stimulation of cardiac fibroblasts with Ang II increased their collagen synthesis in a dose-dependent manner. This effect was blocked by the Ang II receptor antagonist, saralasin. Ang II neither affected the proportion of collagen types nor induced DNA synthesis. Basal collagen synthesis in cardiac fibroblasts from spontaneously hypertensive rats (SHR) was greater than that from normotensive Wistar-Kyoto rats. The responsiveness of collagen production to Ang II was significantly enhanced in cardiac fibroblasts from SHR. These results indicate stimulatory actions of Ang II on collagen synthesis in cardiac fibroblasts, enhanced collagen production in cardiac fibroblasts from SHR, and the hyperresponsiveness of cardiac fibroblasts from SHR to Ang II stimulation. Thus, Ang II may play an important role in collagen accumulation in hypertensive cardiac hypertrophy.

Adhesion durability between dentin pretreated with 10-3 and 4-META/MMA-TBB resin was studied. Reduction of etching periods with 10-3 was not so effective as expected. The weakening of bond strength during immersion in water at 37 degrees C to the dentin pretreated for 1 sec occurred faster than those for either 5 sec or 10 sec. The strength decreased from 12 MPa at 1 day to 9 MPa at 3 months, 3 MPa at 6 months and finally 2 MPa at 1 year in the case of 1 sec pretreated dentin. On the other hand, the strength became half after the storage in water for 1 year in the cases of 5 and 10 sec pretreated dentins. Combination of 10-3 pretreatment and subsequent glutaraldehyde treatment could stabilize the decrease but not completely. SEM and TEM examinations suggested that dentinal collagen exposed by the etching but not entangled and impregnated by poly (4-META-co-MMA) easily deteriorated by water during the longer immersion. Collagen modified with 10-3 and then with glutaraldehyde was also changed by the longer immersion.

EDTA metal ammonium salt solution containing Fe3+, Co3+ or Cu2+ was studied to determine the pretreatment reagent that causes no denaturation of dentin collagen and promotes good adhesion to dentin. After application of EDTA 3-2 (Fe.NH4), EDTA 3-2 (Co.NH4) or EDTA 3-2 (Cu.NH4) at pH 7.4 on the dentin surface, the amount of Ca2+ demineralized and the tensile bond strength were measured. The pretreated dentin surfaces were also observed with SEM. No correlation was obtained between the amount of Ca2+ demineralized and the tensile bond strength. On the EDTA 3-2 (Fe.NH4) treated dentin a small amount of smear remained partially, but the tensile bond strength of 4-META/MMA-TBB resin to the dentin was higher than 13 MPa. This indicates that complete removal of the smear on dentin is not always necessary for better bonding.