Heikki A. Elo

Distribution of 2-methyl-4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid in male rats: evidence for the involvement of the central nervous system in their toxicity.

The effects of different 2-methyl-4-chlorophenoxyacetic acid (MCPA) or 2,4-dichlorophenoxyacetic acid (2,4-D) pretreatments on the distribution of labeled [14C]MCPA or [14C]2,4-D given iv were studied in male rats. Single subcutaneous MCPA or 2,4-D pretreatment increased 14C activity in the brain, cerebrospinal fluid (CSF), liver, muscle, heart, or testis and decreased that in the plasma or kidney, while in the lung 14C activity remained approximately unchanged. Changes in the distribution of 14C activity as well as toxic signs such as myotonia and lethargy appeared within 0.5–1.5 hr after subcutaneous MCPA administration and disappeared in a few days. 14C activities in the brain and CSF of both saline-treated adult and 10- or 21-day-old animals were very low as compared to the other tissues, but in the treated animals these and also absolute MCPA concentration increased to about the level in the muscle or testis. Chronic MCPA exposure had only a slight effect on the distribution of 14C activity. The decreased binding of [14C]MCPA to plasma proteins caused by MCPA pretreatments may explain the increase of 14C activity in many tissues but not the high increase in the brain and CSF during intoxication. The results indicate that at large doses either the influx of MCPA and 2,4-D into the brain is highly increased or their efflux out of the brain is decreased. A potent increase in cerebral 14C activity coincided with the appearance of MCPA intoxication, which suggests that the central nervous system (CNS) is involved in the toxicity of chlorophenoxyacetic acids.

Induction of an antimicrobial biotin-binding egg white protein (avidin) in chick tissues in septicEscherichia coli infection

The induction of avidin in chick tissues was found in septicEscherichia coli infection. Avidin concentrations in the plasma roughly corresponded to those in the other tissues studied which suggests that avidin in chicks is a secretory protein.

Biotin-binding proteins in eggs of oviparous vertebrates

Biotin-binding was found in the egg whites and yolks of all 23 avian species studied, and in a turtle, but the amount varied considerably even in related species. There was no clear correlation in biotin-binding between egg white and yolk in various species. Antigenic determinants of avidin in different species have changed in the course of evolution as compared with those of chicken egg white avidin.

Cumulative superinduction of avidin in the chick oviduct by tissue damage and actinomycin D

Immature chicks were injected daily for nine days with diethylstilbestrol. One group of these chicks was injected with actinomycin D and in another group the oviducts were ligated or pinched with forceps. The chicks were killed at 2 h intervals up to 24 h after the experimental procedure. The avidin content of the oviduct was assayed by the 14C-biotin binding method. The amount of progesterone in the plasma, adrenal gland and ovary was determined by radioimmunoassay. The oviducts of the control animals showed slight or undetectable amounts of avidin. The serum progesterone level (0.71 ± 0.50 ng/ml) of the control animals was similar to that of adults. There was a high concentration of progesterone in the adrenal gland and less in the ovary. In these immature chicks actinomycin D was able to cause superinduction of avidin up to 23 times the control values. Similarly ligation of the oviduct induced avidin synthesis 23–46 and pinching of the oviduct 36 times higher than the controls. The effects of actinomycin D and the ligature were cumulative. Actinomycin D increased the progesterone levels in the serum, ovary and adrenal gland. The ligation caused an increase in plasma progesterone values at 2 h followed by a decrease to control levels at 8 h. Simultaneously the concentration of progesterone decreased in the ovary but increased in the adrenal gland. It is concluded that there are two separate mechanisms for the superinduction of avidin synthesis: one induced by the injection of actinomycin D and the other induced by tissue damage. A combination of evidence supports the concept that the effect of ligation on avidin synthesis is not mediated directly through progesterone, but is caused by a local effect of the tissue damage.

Distribution of [14C]clodronate (dichloromethylene bisphosphonate) disodium in mice.

The distribution of 14C-labeled clodronate (dichloromethylene bisphosphonate), a new bisphosphonate for the treatment of osteolytic bone metastases and hypercalcemia, was studied in mice by whole-body autoradiography and by measuring the 14C activities in various tissues [14C]Clodronate was administered into the tail vein, and its distribution was followed from 5 min to 90 days after the injection. The drug disappeared promptly from the plasma and accumulated intensively in the bone and moderately in the spleen. In both tissues, relatively high radioactivities were measured as late as 90 days after the [14C]clodronate administration. Small amounts of 14C activity were also detected in the liver for 90 days. The results agree well with the previous observations that bisphosphonates deposit rapidly in the bone. Our findings indicate further that clodronate accumulates in the bone and the spleen for several months.

Blood-brain barrier damage by 2-methyl-4-chlorophenoxyacetic acid herbicide in rats

Abstract The integrity of blood-brain barrier (BBB) to serum proteins was studied in rats acutely intoxicated by 2-methyl-4-chlorophenoxyacetic acid (MCPA). Intoxication was produced by giving sodium salt of MCPA sc in single doses of 100, 250, and 500 mg/kg at various intervals before killing the animals. Evans blue, immunohistochemistry of serum proteins, and electron microscopy were used to study the barrier. Extravasations of Evans blue-albumin complex indicating BBB damage were observed with the 250 and 500 mg/kg doses. Lateral cerebral cortex and medulla oblongata were the tissues most consistently affected. Most severe extravasations occurred 4.5 hr after administration of 250 mg/kg MCPA. At 24.5 hr, no extravasation of Evans blue could be demonstrated, which suggests reversibility of the damage. The immunohistochemical demonstration of endogenous albumin or immunoglobulin-G verified the same localizations of the BBB damage. Electron microscopy of the damaged brain areas revealed increased amounts of vesicles in the endothelial cells and local swellings of the basal laminae of the capillaries. As indicated by the extent of extravasation of serum components into the brain, BBB damages appeared within 1.5 hr and showed a marked recovery in 24.5 hr. The damages coincided with the toxic symptoms of the herbicide. Thus the central nervous system was affected by MCPA intoxication.

Avidin induction by tissue injury and inflammation in male and female chickens.

1. The occurrence and inducibility of the biotin-binding egg white protein (avidin) in the chicken is not restricted to the oviduct. 2. Inflammatory treatments (intestinal injury, actinomycin D) induced avidin in a number of tissues of young and adult hens and roosters, but not of female rats and mice. Highest avidin concentrations were found in the organs containing epithelial cells and serous membrane. 3. The expression of the avidin gene by tissue injury and inflammation suggests that avidin has a significant function in the injured and inflamed chicken tissues.

The occurrence and production of avidin: a new conception of the high-affinity biotin-binding protein

The production of avidin, a high-affinity biotin-binding egg-white protein, is not restricted to the avian, amphibian and reptilian oviducts. In the acute phase of inflammation, avidin is synthesized and secreted by various injured tissues in the domestic fowl, both male and female. Also in other avian species and a lizard, injured tissues produce an avidin-like biotin-binding factor. The non-oviductal production of avidin in domestic fowl has a great variety of inducers, for example acute inflammation caused by mechanical or thermal tissue injury, septic bacterial infection and (toxic) drugs, and even retrovirus-induced cell transformation. In culture, chicken embryo fibroblasts and yolk sac macrophages synthesize and secrete avidin. Besides the albumen, avidin may act as an antibacterial protein also in the tissues.

Distribution of three common chlorophenoxyacetic acid herbicides into the rat brain

The distribution of three common14C-labelled chlorophenoxyacetic acid herbicides (2,4-dichlorophenoxyacetic acid or 2,4-D, 2-methyl-4-chlorophenoxyacetic acid or MCPA, 2,4,5-trichlorophenoxyacetic acid or 2,4,5-T) into the different brain areas was studied in rats pretreated with toxic doses of the herbicides (238–475 mg/ kg). Also, their binding to proteins in rat plasma was determined in vitro by increasing the concentrations of chlorophenoxyacetic acids in the incubate from 0 to 1 mg/ml. Both 2,4-D and MCPA pretreatments increased brain concentrations of14C-labelled herbicides more markedly than 2,4,5-T pretreatments did. No essential differences were found in the distribution between the different brain areas. Protein-unbound fractions of 2,4-D and MCPA in the plasma were clearly higher than those of 2,4,5-T but the highest herbicide concentration increased the protein-unbound fraction of 2,4,5-T more (7-13-fold) than of 2,4-D and MCPA (5-fold). The results suggest that the greater increase in the penetration into the brain of 2,4-D and MCPA than of 2,4,5-T during their intoxication is due to some factors other than the changes in their binding to plasma proteins and mere enhanced diffusion through the blood-brain barrier.

Increase in the acute toxicity and brain concentrations of chlorophenoxyacetic acids by probenecid in rats

1. Probenecid increased the acute toxicity of chlorophenoxyacetic acids (2,4-D, 2,4,5-T and MCPA) in rats. 2. Probenecid increased the brain to plasma ratios of all the three 14C-labelled chlorophenoxyacetic acids. The increase was due only partly to the displacement of chlorophenoxyacids from their binding sites in rat plasma proteins by probenecid. 3. Probenecid did not change significantly the intracerebral distribution pattern of 14C-labelled chlorophenoxyacetic acids.