This study finds no change in neonatal T(4) levels despite maternal consumption of drinking water that contains perchlorate at levels in excess of the Environmental Protection Agency (EPA) drinking water equivalent level (24.5 microg/L) based on the National Research Council reference dose (RfD) [0.7 microg/(kg.day)]. Therefore the perchlorate RfD is likely to be protective of thyroid function in neonates of mothers with adequate iodide intake.

A B S T R A C T Plasma fibrinopeptide B (B,81-14 or FPB) immunoreactivity was studied by radioimmunoassay in patients who received intrauterine infusion of hypertonic saline to terminate pregnancy. FPB immunoreactivity increased with thrombin treatment (TIFPB) suggesting the presence of a larger FPBcontaining peptide, since purified FPB is not altered by thrombin, whereas thrombin increases the immunoreactivity of B,B1-42 (which includes FPB) 10-fold. TIFPB immunoreactivity in plasma, drawn 4 h after hypertonic saline infusion eluted from Sephadex G-50 similarly to isolated B,p1-42. Streptokinase, incubated with normal plasma progressively generated TIFPB immunoreactivity, which showed a major component which eluted from Sephadex G-50 similarly to B,B1-42. Streptokinase generated TIFPB much more rapidly in reptilase-treated plasma that contains fibrin I, (which still includes FPB), indicating that fibrin I is preferred over fibrinogen as a substrate for plasmin cleavage of arginine (B,842)-alanine (B,843). Serial studies were then made in 10 patients receiving intrauterine hypertonic saline. Fibrinopeptide A (FPA) levels rose immediately, reached a peak between 1 and 2 h, were declining at4 h, and were normal at24 and 48 h. TIFPB levels rose slightly in the 1st h, reached a peak at 4 h, and had returned to base-line values at 24 h. Serum fibrinogen degradation product levels were unchanged at 1 h, reached their highest level at 4 h, and were still markedly elevated at 24 and 48 h. Fibrinogen levels dropped slightly being lowest at 4 and 24 h. Platelet counts declined in parallel with the fibrinogen levels over the first 4 h, but continued to decrease through 48 h. Beta thromboglobulin (,fTG) levels generally paralleled FPA levels whereas platelet factor 4 (PF4) levels showed only slight changes. The data indicate that immediately after intrauterine hypertonic saline Dr. Kaplan is a Senior Investigator of the New York Heart Association.

Thrombin cleaves fibrinogen in two steps producing fibrin I and fibrinopeptide A(FPA) and then fibrin II and fibrinopeptide B(FPB). Plasmin cleaves the Aα chain and the N-terminal Bβ chain to form fragment X. Radioiimminoassay of plasma FPA reflects fibrin I formation. A modified FPB assay detects plasm in-produced Bβ1-42, reflecting fragment X formation. Sequential changes have been studied in saline abortion and in venous thrombosis. Following intra-uterine infusion of hypertonic saline to interrupt pregnancy, FPA levels rose immediately from 1 to 18 pmol/ml in 60 minutes, and after 2 hours began to slowly decline to the baseline level. Bβ1-42 levels rose rapidly after the first hour to reach 67 pmol/ml at 4 hours. Thus fibrin I was formed and then fragment X. In post-surgical patients FPA levels rose and exceeded Bβ1-42 levels for several days preceding thrombosis indicated by 125I-fibrinogen scanning and confirmed by venography. These results suggest that following injury thrombin forms fibrin I. Each fibrin I molecule is then either cleaved by thrombin to form fibrin II or by plasmin to form fragment X. The balance between thrombin and plasmin proteolysis of the N-terminal Bβ chain may be critical. Normally sufficient fibrin II formation occurs for effective hemostasis. Thrombosis occurs with excessive thrombin action and fibrin II formation. Slow thrombin formation as in hemophilia results in preferential formation of fragment X and ineffective hemostasis.